iOS 第二梯隊面試敗北感悟 | 掘金技術徵文

Castie1發表於2018-04-13

GitHub Repo：coderZsq.target.swift
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日常扯淡

從去年開始, 我就一直有嘗試的面試些大公司, 因為對於一個半路出家(非計算機專業), 靠著MJ視訊入門的iOS菜雞玩家, 經過了3年的摸爬滾打, 終於也漸漸的可以做一些簡單的前端, 後端, 移動端的互動, 但想要繼續深入就感覺瓶頸越發的明顯, 基礎的薄弱導致很難上升, 所以能夠進入一家大型成熟網際網路公司就成為了我最近的目標, 原因很簡單, 這是最為有效的學習成長的方式.

去年7月, 第一次面試大公司: 餓了麼, 收到大公司的召喚非常的興奮, 覺得自己翻身的機會終於要來了, 興沖沖的跑去面試, 以為會和一般初級iOS面試的題目相同, 沒有做任何的準備, 其實也不知道準備什麼, 記得那時候聊的是:

UI方面: 如何避免卡頓掉幀, 非同步渲染.
效能方面: 效能優化, Vsync, CPU / GPU
網路方面: 如何進行請求快取策略.
安全方面: lild重簽名, Mach-O.
前端方面: 如何避免DOM重繪.
後端方面: 如何進行負載均衡的處理.

還有一些極端的情況, 由於時間久遠已經記不太清了, 反正這次面試給我的感覺就是, 靠... 我簡直就是個垃圾啊~ 當時記得內推我的架構師建議我紮實一下iOS的基本功, 然後就推薦了基本書: 計算機網路, 作業系統原理, HTTP權威指南, TCP/IP權威指南, 深入解析Max OS X & iOS 作業系統... 這些書, 除了HTTP權威指南我咬著牙看完了, 其他的對於我來說簡直就是天書, 根本消化不良啊.

去年12月, 第二次面試大公司: 京東, 由於有了上一次的經驗, 我變得非常的淡定, 知道自己肯定會被大公司所淘汰, 和優等專業生有著不可逾越的天塹, 比較吃驚的是, 進入京東的大樓需要用身份證換取臨時門禁... 那時候的面試題就比餓了麼的柔和的多了, 雖然當時還是回答不出.

Runtime: isa, 訊息轉發, 弱引用表.
Runloop: mode, timer.
Block: __block, __forwording.
Property: assign, weak, copy.
Category: assoc, load

現在想想, 這TM才是面試iOS啊, 只可惜, 那時候並不具備這些知識, 可惜了了. 之後我就對C++, ASM, Linux, 這三方面進行了學習, 也學習了些MACH-O, 逆向的相關的知識, 以備後面的面試機會.

第三次就是這週三面試第二梯隊了, 我準備了所有我能夠準備的面試題內容, 底層原理, 逆向安全, 多執行緒與鎖, 記憶體佈局, UI效能優化等, 果不其然, 足足1個小時的電話面試, 我輕鬆通過, 問的就是些我準備好的底層知識, 讓我覺得機會終於來了, 可是.... 當我現場面試後... 題目全部是上機題...

設計一個網路框架, 如何進行不同資料解析的設計(header, body), 並能夠進行自定義, 重連機制如何處理, 狀態碼錯誤轉發機制的處理, 如何避免回撥地獄, 實現Promise的自實現.
根據UIControl實現UIButton....
找到兩個排序陣列的中位數...
pow(double, double)函式的自實現....

果然,網路, UI, 演算法... 好吧, 第一次做上機題, 瞬間就蒙了... 然後就是面試官在旁邊不停的笑... 不停的笑... 可能是他對我友好的一種方式吧... 最後的面試結論是, 我的知識面還是比較廣的, 做過的東西也是挺多的, 但是在知識深度方面還是比較欠缺.

後來得知, 他們招聘的是技術專家的職級, 覺得我的技術水平達不到要求, 不能給與錄取, 當然被拒我是當場就知道了, 也覺得美團和餓了麼的兩次面試經歷都和我的水平相差甚遠... 可是, 我只是想進入大公司學習, 就一定要成為專家才行麼? 現在初中高階, 資深都不需要了, 直接專家麼..., 我的獵頭朋友和我說, 3-1的級別就是對標阿里P6/P7, 我選擇去死啊.....

有了這次的面試經驗後, 我的策略也發生了改變, 不再追求大公司的光環了, 做人開心一點不好麼, 非要像機器一樣思考? 活的像個演算法一樣是不是感覺缺少了些重要的東西? 和朋友們吹吹牛逼的日子不快活麼, 偏要用功學習? 這裡想到了最近聽到的兩句話, 最好的產品體驗就是要讓使用者不用思考, 認知即痛苦, 無知即極樂, 人真是矛盾, 價值觀的一念之差, 差之毫釐失之千里啊....

面試題1 自實現pow(double, double)

這道題目上機的時候非常的蒙, 因為冪是double, 完全不知道如何下手, 面試官就降低難度使用整型.

解法1

func _pow_1(_ base: Int, _ exponent: Int) -> Int {

    if exponent < 0 {
        return 0
    }
    if exponent == 0 {
        return 0
    }
    if exponent == 1 {
        return base
    }
    
    var result = base
    for _ in 1..<exponent {
        result *= base
    }
    return result
}
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然後, 第一次做演算法題的我, 只能想到通過最為粗糙的辦法解答, 就是一個迴圈, 我也知道這不是面試官所期許的答案, 但這有什麼辦法呢...

解法2

func _pow_2(_ base: Double, _ exponent: Int) -> Double {
    
    if exponent < 0 {
        return 0
    }
    if exponent == 0 {
        return 0
    }
    var ans:Double = 1, last_pow = base, exp = exponent
    
    while exp > 0 {
        if (exp & 1) != 0 {
            ans = ans * last_pow
        }
        exp = exp >> 1
        last_pow = last_pow * last_pow
    }
    return ans
}
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這個是我在網上翻閱資料後的另一種看似比較好的解答方式.

解法3

func _pow_3(_ base: Double, _ exponent: Int) -> Double {

    var isNegative = false
    var exp = exponent
    if exp < 0 {
        isNegative = true
        exp = -exp
    }
    let result = _pow_2(base, exp)
    return isNegative ? 1 / result : result
}
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這個僅僅是加了一個負值判斷.... 但是冪是double的仍然是毫無頭緒, 需要請大佬和大神不吝賜教.

面試題2 findMedianSortedArrays

這是一道LeetCode的原題, 但是我至今還沒有刷過演算法題庫... 也是平生第一次面試的時候遇到演算法題. 題目的意思是找到兩個排序陣列的中位數.

解法1

func findMedianSortedArrays_1(_ array1: [Int], _ array2: [Int]) -> Double {
    
    var array = [Int]()
    array.append(contentsOf: array1)
    array.append(contentsOf: array2)
    
    quickSort(list: &array)
    
    let b = array.count % 2
    let c = array.count
    var result = 0.0;
    if  b == 1  {
        result = Double(array[c / 2])
    } else {
        let n1 = array[c / 2 - 1]
        let n2 = array[c / 2]
        result = Double((n1 + n2)) / 2.0
    }
    
    return result
}
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第一次做演算法題, 只能無視演算法複雜度, 能夠完成就算是不錯了, 要什麼自行車...

解法2

func findMedianSortedArrays_2(_ array1: [Int], _ array2: [Int]) -> Double {
    
    let c1 = array1.count, c2 = array2.count
    var a1 = array1, a2 = array2
    if c1 <= 0 && c2 <= 0 {
        return 0.0
    }
    
    func findKth(_ nums1: inout [Int], i: Int, _ nums2: inout [Int], j: Int, k: Int) -> Double {
        if nums1.count - i > nums2.count - j {
            return findKth(&nums2, i: j, &nums1, j: i, k: k)
        }
        if nums1.count == i {
            return Double(nums2[j + k - 1])
        }
        if k == 1 {
            return Double(min(nums1[i], nums2[j]))
        }
        let pa = min(i + k / 2, nums1.count), pb = j + k - pa + i
        if nums1[pa - 1] < nums2[pb - 1] {
            return findKth(&nums1, i: pa, &nums2, j: j, k: k - pa + i)
        } else if nums1[pa - 1] > nums2[pb - 1] {
            return findKth(&nums1, i: i, &nums2, j: pb, k: k - pb + j)
        } else {
            return Double(nums1[pa - 1])
        }
    }
    
    let total = c1 + c2
    if total % 2 == 1 {
        return findKth(&a1, i: 0, &a2, j: 0, k: total / 2 + 1)
    } else {
        return (findKth(&a1, i: 0, &a2, j: 0, k: total / 2) + findKth(&a1, i: 0, &a2, j: 0, k: total / 2 + 1)) / 2.0
    }
}
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這個是我在網上查資料的時候的答案... 還沒理清是個什麼思路, 反正面試官提示分而治之, 掐頭去尾... 也不知道是不是最優演算法.

解法3

func findMedianSortedArrays_3(_ array1: [Int], _ array2: [Int]) -> Double {
    
    let total = array1.count + array2.count
    let index = total / 2
    let count = array1.count < array2.count ? array2.count : array1.count
    var array = [Int]()
    
    var i = 0, j = 0;
    for _ in 0...count {
        if array.count >= index + 1 {
            break
        }
        if array1[i] < array2[j] {
            array.append(array1[i])
            i += 1
        } else {
            array.append(array2[j])
            j += 1
        }
    }
    return total % 2 == 1 ? Double(array[index]) : Double(array[index] + array[index - 1]) * 0.5
}
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這個是請教霜神(@halfrost-一縷殤流化隱半邊冰霜)後給的思路, 的確很好實現. 但霜神謙虛的說不是最優解....

奇數測試

var array1 = randomList(1000001)
var array2 = randomList(1000000)
quickSort(list: &array1)
quickSort(list: &array2)
print(findMedianSortedArrays_1(array1, array2))
print(findMedianSortedArrays_2(array1, array2))
print(findMedianSortedArrays_3(array1, array2))
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--- scope of: findMedianSortedArrays ---
500045.0
500045.0
500045.0
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偶數測試

var array1 = randomList(1000001)
var array2 = randomList(1000000)
quickSort(list: &array1)
quickSort(list: &array2)
print(findMedianSortedArrays_1(array1, array2))
print(findMedianSortedArrays_2(array1, array2))
print(findMedianSortedArrays_3(array1, array2))
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--- scope of: findMedianSortedArrays ---
499665.5
499665.5
499665.5
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耗時比較

--- scope of: findMedianSortedArrays_1 ---
timing: 2.50845623016357
--- scope of: findMedianSortedArrays_2 ---
timing: 1.28746032714844e-05
--- scope of: findMedianSortedArrays_3 ---
timing: 0.0358490943908691
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可以看出網上查資料的答案是三種解法裡效能最高的演算法, 霜神的思路和網上的答案差了三個數量級, 而我寫的差了五個數量級.... 果然我寫的果然是最為垃圾的演算法....

解法4

@discardableResult func findMedianSortedArrays_4(_ array1: [Int], _ array2: [Int]) -> Double {
    
    if array1.count == 0 {
        if array2.count % 2 == 1 {
            return Double(array2[array2.count / 2])
        } else {
            return Double(array2[array2.count / 2] + array2[array2.count / 2 - 1]) * 0.5
        }
    } else if array2.count == 0 {
        if array1.count % 2 == 1 {
            return Double(array1[array1.count / 2])
        } else {
            return Double(array1[array1.count / 2] + array1[array1.count / 2 - 1]) * 0.5
        }
    }
    
    let total = array1.count + array2.count
    let count = array1.count < array2.count ? array1.count : array2.count
    let odd = total % 2 == 1
    
    var i = 0, j = 0, f = 1, m1 = 0.0, m2 = 0.0, result = 0.0;
    for _ in 0...count {
        if odd { array1[i] < array2[j] ? (i += 1) : (j += 1) }
        if f >= total / 2 {
            if odd {
                result = array1[i] < array2[j] ? Double(array1[i]) : Double(array2[j])
            } else {
                if array1[i] < array2[j] {
                    m1 = Double(array1[i])
                    if (i + 1) < array1.count && array1[i + 1] < array2[j] {
                        m2 = Double(array1[i + 1])
                    } else {
                        m2 = Double(array2[j])
                    }
                } else {
                    m1 = Double(array2[j])
                    if (j + 1) < array2.count && array2[j + 1] < array1[i] {
                        m2 = Double(array2[j + 1])
                    } else {
                        m2 = Double(array1[i])
                    }
                }
                result = (m1 + m2) * 0.5
            }
            break
        }
        if !odd { array1[i] < array2[j] ? (i += 1) : (j += 1) }
        f += 1
    }
    return result
}
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--- scope of: findMedianSortedArrays_3 ---
timing: 0.0358932018280029
--- scope of: findMedianSortedArrays_4 ---
timing: 0.0241639614105225
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沿著霜神的思路和麵試官給的提示, 給出了上面的演算法, 但是解法3的數量級是相同的

面試題3 UIContorl -> UIButton

protocol ButtonInterface {
    func setTitle(_ title: String);
    func setTitleColor(_ titleColor: UIColor);
    func setTitleEdgeInsets(_ edgeInsets: UIEdgeInsets);
    func setImage(_ image: UIImage);
    func setBackgroundImage(_ image: UIImage);
    func setImageEdgeInsets(_ edgeInsets: UIEdgeInsets);
}

class Button: UIControl, ButtonInterface { 

}
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以上就是面試時候的原題, 一開始根本不知道是要讓我做些什麼, 說是隻要讓我把上面的方法全部實現就好了, 就像實現一個自己的UIButton... 一開始, 我以為是要我用CALayer來實現, 嚇的我瑟瑟發抖... 還好不是... 然後, 我就按照自己平時自定義控制元件的寫法, 寫了一個UIImageView, 一個UILabel, 然後佈局賦值... 就看到面試官對著我笑著說, 你以為這道題這麼簡單麼... 這麼簡單麼...

然後說, 你知道UIButton setTitle的時候才會建立UILabel, setImage的時候才會建立UIImageView, 你為什麼吧frame給寫死... 不知道UIView有sizeToFit麼, 你怎麼不實現sizeThatFits, 你是完全不會用吧... 你知道UIButton用AutoLayout佈局的時候只要設定origin座標, 寬高就可以自適應了, 你自定義的時候怎麼不實現呢? setBackgroundImage和setImageEdgeInsets你就不要做了吧, 反正你也不會...

我想說的是,誰沒事放著UIButton不用, 用UIContorl這種東西... 就為了一個target-action的設計模式麼... 我每次在想思路的時候一直打斷我, 可能這是面試官的一種策略吧... 算了不吐槽了, 還是盡力實現吧.

import UIKit

protocol ButtonInterface {
    func setTitle(_ title: String);
    func setTitleColor(_ titleColor: UIColor);
    func setTitleEdgeInsets(_ edgeInsets: UIEdgeInsets);
    func setImage(_ image: UIImage);
    func setBackgroundImage(_ image: UIImage);
    func setImageEdgeInsets(_ edgeInsets: UIEdgeInsets);
}

class Button: UIControl, ButtonInterface {

    lazy var titleLabel: UILabel = UILabel()
    lazy var imageView: UIImageView = UIImageView()
    lazy var backgroundImageView: UIImageView = UIImageView()
    
    var titleLabelIsCreated = false
    var imageViewIsCreated = false
    var backgroundImageViewCreated = false
    
    internal func setTitle(_ text: String) {
        if !titleLabelIsCreated {
            addSubview(titleLabel)
            titleLabelIsCreated = true
        }
        titleLabel.text = text
    }

    internal func setTitleColor(_ textColor: UIColor) {
        if !titleLabelIsCreated {
            return
        }
        titleLabel.textColor = textColor
    }
    
    internal func setTitleEdgeInsets(_ edgeInsets: UIEdgeInsets) {
        if !titleLabelIsCreated {
            return
        }
    }
    
    internal func setImage(_ image: UIImage) {
        if !imageViewIsCreated {
            addSubview(imageView)
            imageViewIsCreated = true
        }
        imageView.image = image
    }
    
    internal func setBackgroundImage(_ image: UIImage) {
        if !backgroundImageViewCreated {
            addSubview(backgroundImageView)
            insertSubview(backgroundImageView, at: 0)
            backgroundImageViewCreated = true
        }
        backgroundImageView.image = image
    }
    
    internal func setImageEdgeInsets(_ edgeInsets: UIEdgeInsets) {
        if !imageViewIsCreated {
            return
        }
    }
    
    override func sizeThatFits(_ size: CGSize) -> CGSize {
        if titleLabelIsCreated && !imageViewIsCreated && !backgroundImageViewCreated {
            let text: NSString? = titleLabel.text as NSString?
            let titleLabelW: CGFloat = text?.boundingRect(with: CGSize(width: CGFloat(MAXFLOAT), height: bounds.height), options: NSStringDrawingOptions.usesLineFragmentOrigin, attributes: [NSAttributedStringKey.font : titleLabel.font], context: nil).size.width ?? 0.0
            let titleLabelH: CGFloat = text?.boundingRect(with: CGSize(width: titleLabelW, height: CGFloat(MAXFLOAT)), options: NSStringDrawingOptions.usesLineFragmentOrigin, attributes: [NSAttributedStringKey.font : titleLabel.font], context: nil).size.height ?? 0.0
            return CGSize(width: titleLabelW, height: titleLabelH + 10)
        } else if !titleLabelIsCreated && imageViewIsCreated {
            return imageView.image?.size ?? CGSize.zero
        } else if titleLabelIsCreated && imageViewIsCreated {
            let text: NSString? = titleLabel.text as NSString?
            let titleLabelW: CGFloat = text?.boundingRect(with: CGSize(width: CGFloat(MAXFLOAT), height: bounds.height), options: NSStringDrawingOptions.usesLineFragmentOrigin, attributes: [NSAttributedStringKey.font : titleLabel.font], context: nil).size.width ?? 0.0
            let titleLabelH: CGFloat = text?.boundingRect(with: CGSize(width: titleLabelW, height: CGFloat(MAXFLOAT)), options: NSStringDrawingOptions.usesLineFragmentOrigin, attributes: [NSAttributedStringKey.font : titleLabel.font], context: nil).size.height ?? 0.0
            let imageViewW: CGFloat = imageView.image?.size.width ?? 0.0
            let imageViewH: CGFloat = imageView.image?.size.height ?? 0.0
            return CGSize(width: titleLabelW + imageViewW, height: imageViewH > titleLabelH ? imageViewH : titleLabelH)
        } else {
            return backgroundImageView.image?.size ?? CGSize.zero
        }
    }
    
    override func layoutSubviews() {
        super.layoutSubviews()

        if titleLabelIsCreated && !imageViewIsCreated {
            titleLabel.frame = bounds
            titleLabel.textAlignment = .center
        } else if !titleLabelIsCreated && imageViewIsCreated {
            let y: CGFloat = 0;
            let width: CGFloat = imageView.image?.size.width ?? 0;
            let x: CGFloat = (bounds.width - width) * 0.5;
            let height: CGFloat = bounds.height;
            imageView.frame = CGRect(x: x, y: y, width: width, height: height)
        } else if titleLabelIsCreated && imageViewIsCreated {
            let imageViewY: CGFloat = 0;
            let imageViewW: CGFloat = imageView.image?.size.width ?? 0;
            let imageViewH: CGFloat = bounds.height;
            let text: NSString? = titleLabel.text as NSString?
            let titleLabelW: CGFloat = text?.boundingRect(with: CGSize(width: CGFloat(MAXFLOAT), height: bounds.height), options: NSStringDrawingOptions.usesLineFragmentOrigin, attributes: [NSAttributedStringKey.font : titleLabel.font], context: nil).size.width ?? 0.0
            let titleLabelH: CGFloat = text?.boundingRect(with: CGSize(width: titleLabelW, height: CGFloat(MAXFLOAT)), options: NSStringDrawingOptions.usesLineFragmentOrigin, attributes: [NSAttributedStringKey.font : titleLabel.font], context: nil).size.height ?? 0.0
            let imageViewX: CGFloat = (bounds.width - imageViewW - titleLabelW) * 0.5;
            let titleLabelX: CGFloat = imageViewX + imageViewW
            let titleLabelY = (bounds.height - titleLabelH) * 0.5
            titleLabel.frame = CGRect(x: titleLabelX, y: titleLabelY, width: titleLabelW, height: titleLabelH)
            imageView.frame = CGRect(x: imageViewX, y: imageViewY, width: imageViewW, height: imageViewH)
        }
        
        if backgroundImageViewCreated {
            backgroundImageView.frame = bounds
        }
    }
}
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雖然實現了部分的功能, 但是AutoLayout和EdgeInsets的功能還是沒有思路, 還請各位大佬解惑.

測試對比

我們用自己自實現的Button和UIButton進行對比.

class ViewController: UIViewController {

    override func loadView() {
        super.loadView();
        
        let uibutton = UIButton()
        uibutton.layer.borderWidth = 1
        uibutton.layer.borderColor = UIColor.black.cgColor
        
        uibutton.frame = CGRect(x: 0, y: 100, width: view.bounds.width, height: 40)
        uibutton.setTitle("github.com/coderZsq", for: .normal)
        uibutton.setTitleColor(.red, for: .normal)
        uibutton.titleEdgeInsets = UIEdgeInsetsMake(0, 0, 0, 0)
        uibutton.setImage(UIImage(named: "avatar"), for: .normal)
        uibutton.setBackgroundImage(UIImage(named: "avatar"), for: .normal)
        uibutton.imageEdgeInsets = UIEdgeInsetsMake(-10, -10, -10, -10)
        view.addSubview(uibutton)
        uibutton.sizeToFit()
        
        let button = Button()
        button.layer.borderWidth = 1
        button.layer.borderColor = UIColor.black.cgColor
        
        button.frame = CGRect(x: 0, y: 350, width: view.bounds.width, height: 40)
        button.setTitle("github.com/coderZsq")
        button.setTitleColor(.red)
        button.setTitleEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
        button.setImage(UIImage(named: "avatar") ?? UIImage());
        button.setBackgroundImage(UIImage(named: "avatar") ?? UIImage())
        button.setImageEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
        view.addSubview(button)
        button.sizeToFit()
    }
}
複製程式碼

zero impl


        let uibutton = UIButton()
        uibutton.layer.borderWidth = 1
        uibutton.layer.borderColor = UIColor.black.cgColor
        
        uibutton.frame = CGRect(x: 0, y: 100, width: view.bounds.width, height: 40)
//        uibutton.setTitle("github.com/coderZsq", for: .normal)
//        uibutton.setTitleColor(.red, for: .normal)
//        uibutton.titleEdgeInsets = UIEdgeInsetsMake(0, 0, 0, 0)
//        uibutton.setImage(UIImage(named: "avatar"), for: .normal)
//        uibutton.setBackgroundImage(UIImage(named: "avatar"), for: .normal)
//        uibutton.imageEdgeInsets = UIEdgeInsetsMake(-10, -10, -10, -10)
        view.addSubview(uibutton)
//        uibutton.sizeToFit()
        
        let button = Button()
        button.layer.borderWidth = 1
        button.layer.borderColor = UIColor.black.cgColor
        
        button.frame = CGRect(x: 0, y: 350, width: view.bounds.width, height: 40)
//        button.setTitle("github.com/coderZsq")
//        button.setTitleColor(.red)
//        button.setTitleEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
//        button.setImage(UIImage(named: "avatar") ?? UIImage());
//        button.setBackgroundImage(UIImage(named: "avatar") ?? UIImage())
//        button.setImageEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
        view.addSubview(button)
//        button.sizeToFit()

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setTitle && setTitleColor

        let uibutton = UIButton()
        uibutton.layer.borderWidth = 1
        uibutton.layer.borderColor = UIColor.black.cgColor
        
        uibutton.frame = CGRect(x: 0, y: 100, width: view.bounds.width, height: 40)
        uibutton.setTitle("github.com/coderZsq", for: .normal)
        uibutton.setTitleColor(.red, for: .normal)
//        uibutton.titleEdgeInsets = UIEdgeInsetsMake(0, 0, 0, 0)
//        uibutton.setImage(UIImage(named: "avatar"), for: .normal)
//        uibutton.setBackgroundImage(UIImage(named: "avatar"), for: .normal)
//        uibutton.imageEdgeInsets = UIEdgeInsetsMake(-10, -10, -10, -10)
        view.addSubview(uibutton)
//        uibutton.sizeToFit()
        
        let button = Button()
        button.layer.borderWidth = 1
        button.layer.borderColor = UIColor.black.cgColor
        
        button.frame = CGRect(x: 0, y: 350, width: view.bounds.width, height: 40)
        button.setTitle("github.com/coderZsq")
        button.setTitleColor(.red)
//        button.setTitleEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
//        button.setImage(UIImage(named: "avatar") ?? UIImage());
//        button.setBackgroundImage(UIImage(named: "avatar") ?? UIImage())
//        button.setImageEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
        view.addSubview(button)
//        button.sizeToFit()
    }
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setTitle && setTitleColor && sizeToFit

        let uibutton = UIButton()
        uibutton.layer.borderWidth = 1
        uibutton.layer.borderColor = UIColor.black.cgColor
        
        uibutton.frame = CGRect(x: 0, y: 100, width: view.bounds.width, height: 40)
        uibutton.setTitle("github.com/coderZsq", for: .normal)
        uibutton.setTitleColor(.red, for: .normal)
//        uibutton.titleEdgeInsets = UIEdgeInsetsMake(0, 0, 0, 0)
//        uibutton.setImage(UIImage(named: "avatar"), for: .normal)
//        uibutton.setBackgroundImage(UIImage(named: "avatar"), for: .normal)
//        uibutton.imageEdgeInsets = UIEdgeInsetsMake(-10, -10, -10, -10)
        view.addSubview(uibutton)
        uibutton.sizeToFit()
        
        let button = Button()
        button.layer.borderWidth = 1
        button.layer.borderColor = UIColor.black.cgColor
        
        button.frame = CGRect(x: 0, y: 350, width: view.bounds.width, height: 40)
        button.setTitle("github.com/coderZsq")
        button.setTitleColor(.red)
//        button.setTitleEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
//        button.setImage(UIImage(named: "avatar") ?? UIImage());
//        button.setBackgroundImage(UIImage(named: "avatar") ?? UIImage())
//        button.setImageEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
        view.addSubview(button)
        button.sizeToFit()
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setImage

        let uibutton = UIButton()
        uibutton.layer.borderWidth = 1
        uibutton.layer.borderColor = UIColor.black.cgColor
        
        uibutton.frame = CGRect(x: 0, y: 100, width: view.bounds.width, height: 40)
//        uibutton.setTitle("github.com/coderZsq", for: .normal)
//        uibutton.setTitleColor(.red, for: .normal)
//        uibutton.titleEdgeInsets = UIEdgeInsetsMake(0, 0, 0, 0)
        uibutton.setImage(UIImage(named: "avatar"), for: .normal)
//        uibutton.setBackgroundImage(UIImage(named: "avatar"), for: .normal)
//        uibutton.imageEdgeInsets = UIEdgeInsetsMake(-10, -10, -10, -10)
        view.addSubview(uibutton)
//        uibutton.sizeToFit()
        
        let button = Button()
        button.layer.borderWidth = 1
        button.layer.borderColor = UIColor.black.cgColor
        
        button.frame = CGRect(x: 0, y: 350, width: view.bounds.width, height: 40)
//        button.setTitle("github.com/coderZsq")
//        button.setTitleColor(.red)
//        button.setTitleEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
        button.setImage(UIImage(named: "avatar") ?? UIImage());
//        button.setBackgroundImage(UIImage(named: "avatar") ?? UIImage())
//        button.setImageEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
        view.addSubview(button)
//        button.sizeToFit()
複製程式碼

setImage && sizeToFit

        let uibutton = UIButton()
        uibutton.layer.borderWidth = 1
        uibutton.layer.borderColor = UIColor.black.cgColor
        
        uibutton.frame = CGRect(x: 0, y: 100, width: view.bounds.width, height: 40)
//        uibutton.setTitle("github.com/coderZsq", for: .normal)
//        uibutton.setTitleColor(.red, for: .normal)
//        uibutton.titleEdgeInsets = UIEdgeInsetsMake(0, 0, 0, 0)
        uibutton.setImage(UIImage(named: "avatar"), for: .normal)
//        uibutton.setBackgroundImage(UIImage(named: "avatar"), for: .normal)
//        uibutton.imageEdgeInsets = UIEdgeInsetsMake(-10, -10, -10, -10)
        view.addSubview(uibutton)
        uibutton.sizeToFit()
        
        let button = Button()
        button.layer.borderWidth = 1
        button.layer.borderColor = UIColor.black.cgColor
        
        button.frame = CGRect(x: 0, y: 350, width: view.bounds.width, height: 40)
//        button.setTitle("github.com/coderZsq")
//        button.setTitleColor(.red)
//        button.setTitleEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
        button.setImage(UIImage(named: "avatar") ?? UIImage());
//        button.setBackgroundImage(UIImage(named: "avatar") ?? UIImage())
//        button.setImageEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
        view.addSubview(button)
        button.sizeToFit()
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setBackgroundImage

        let uibutton = UIButton()
        uibutton.layer.borderWidth = 1
        uibutton.layer.borderColor = UIColor.black.cgColor
        
        uibutton.frame = CGRect(x: 0, y: 100, width: view.bounds.width, height: 40)
//        uibutton.setTitle("github.com/coderZsq", for: .normal)
//        uibutton.setTitleColor(.red, for: .normal)
//        uibutton.titleEdgeInsets = UIEdgeInsetsMake(0, 0, 0, 0)
//        uibutton.setImage(UIImage(named: "avatar"), for: .normal)
        uibutton.setBackgroundImage(UIImage(named: "avatar"), for: .normal)
//        uibutton.imageEdgeInsets = UIEdgeInsetsMake(-10, -10, -10, -10)
        view.addSubview(uibutton)
//        uibutton.sizeToFit()
        
        let button = Button()
        button.layer.borderWidth = 1
        button.layer.borderColor = UIColor.black.cgColor
        
        button.frame = CGRect(x: 0, y: 350, width: view.bounds.width, height: 40)
//        button.setTitle("github.com/coderZsq")
//        button.setTitleColor(.red)
//        button.setTitleEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
//        button.setImage(UIImage(named: "avatar") ?? UIImage());
        button.setBackgroundImage(UIImage(named: "avatar") ?? UIImage())
//        button.setImageEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
        view.addSubview(button)
//        button.sizeToFit()

複製程式碼

這裡, 我們看到和系統的實現不一樣, 因為我直接在渲染(display)設定了bitmap, 而不是像系統新增了一個新的view. 這樣的效能消耗會少些... (以修改為了下面的問題)

setBackgroundImage && sizeToFit

        let uibutton = UIButton()
        uibutton.layer.borderWidth = 1
        uibutton.layer.borderColor = UIColor.black.cgColor
        
        uibutton.frame = CGRect(x: 0, y: 100, width: view.bounds.width, height: 40)
//        uibutton.setTitle("github.com/coderZsq", for: .normal)
//        uibutton.setTitleColor(.red, for: .normal)
//        uibutton.titleEdgeInsets = UIEdgeInsetsMake(0, 0, 0, 0)
//        uibutton.setImage(UIImage(named: "avatar"), for: .normal)
        uibutton.setBackgroundImage(UIImage(named: "avatar"), for: .normal)
//        uibutton.imageEdgeInsets = UIEdgeInsetsMake(-10, -10, -10, -10)
        view.addSubview(uibutton)
        uibutton.sizeToFit()
        
        let button = Button()
        button.layer.borderWidth = 1
        button.layer.borderColor = UIColor.black.cgColor
        
        button.frame = CGRect(x: 0, y: 350, width: view.bounds.width, height: 40)
//        button.setTitle("github.com/coderZsq")
//        button.setTitleColor(.red)
//        button.setTitleEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
//        button.setImage(UIImage(named: "avatar") ?? UIImage());
        button.setBackgroundImage(UIImage(named: "avatar") ?? UIImage())
//        button.setImageEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
        view.addSubview(button)
        button.sizeToFit()

複製程式碼

setTitle && setTitleColor && setImage

        let uibutton = UIButton()
        uibutton.layer.borderWidth = 1
        uibutton.layer.borderColor = UIColor.black.cgColor
        
        uibutton.frame = CGRect(x: 0, y: 100, width: view.bounds.width, height: 40)
        uibutton.setTitle("github.com/coderZsq", for: .normal)
        uibutton.setTitleColor(.red, for: .normal)
//        uibutton.titleEdgeInsets = UIEdgeInsetsMake(0, 0, 0, 0)
        uibutton.setImage(UIImage(named: "avatar"), for: .normal)
//        uibutton.setBackgroundImage(UIImage(named: "avatar"), for: .normal)
//        uibutton.imageEdgeInsets = UIEdgeInsetsMake(-10, -10, -10, -10)
        view.addSubview(uibutton)
//        uibutton.sizeToFit()
        
        let button = Button()
        button.layer.borderWidth = 1
        button.layer.borderColor = UIColor.black.cgColor
        
        button.frame = CGRect(x: 0, y: 350, width: view.bounds.width, height: 40)
        button.setTitle("github.com/coderZsq")
        button.setTitleColor(.red)
//        button.setTitleEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
        button.setImage(UIImage(named: "avatar") ?? UIImage());
//        button.setBackgroundImage(UIImage(named: "avatar") ?? UIImage())
//        button.setImageEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
        view.addSubview(button)
//        button.sizeToFit()

複製程式碼

setTitle && setTitleColor && setImage && sizeToFit

        let uibutton = UIButton()
        uibutton.layer.borderWidth = 1
        uibutton.layer.borderColor = UIColor.black.cgColor
        
        uibutton.frame = CGRect(x: 0, y: 100, width: view.bounds.width, height: 40)
        uibutton.setTitle("github.com/coderZsq", for: .normal)
        uibutton.setTitleColor(.red, for: .normal)
//        uibutton.titleEdgeInsets = UIEdgeInsetsMake(0, 0, 0, 0)
        uibutton.setImage(UIImage(named: "avatar"), for: .normal)
//        uibutton.setBackgroundImage(UIImage(named: "avatar"), for: .normal)
//        uibutton.imageEdgeInsets = UIEdgeInsetsMake(-10, -10, -10, -10)
        view.addSubview(uibutton)
        uibutton.sizeToFit()
        
        let button = Button()
        button.layer.borderWidth = 1
        button.layer.borderColor = UIColor.black.cgColor
        
        button.frame = CGRect(x: 0, y: 350, width: view.bounds.width, height: 40)
        button.setTitle("github.com/coderZsq")
        button.setTitleColor(.red)
//        button.setTitleEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
        button.setImage(UIImage(named: "avatar") ?? UIImage());
//        button.setBackgroundImage(UIImage(named: "avatar") ?? UIImage())
//        button.setImageEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
        view.addSubview(button)
        button.sizeToFit()
複製程式碼

setTitle && setTitleColor && setBackgroundImage


        let uibutton = UIButton()
        uibutton.layer.borderWidth = 1
        uibutton.layer.borderColor = UIColor.black.cgColor
        
        uibutton.frame = CGRect(x: 0, y: 100, width: view.bounds.width, height: 40)
        uibutton.setTitle("github.com/coderZsq", for: .normal)
        uibutton.setTitleColor(.red, for: .normal)
//        uibutton.titleEdgeInsets = UIEdgeInsetsMake(0, 0, 0, 0)
//        uibutton.setImage(UIImage(named: "avatar"), for: .normal)
        uibutton.setBackgroundImage(UIImage(named: "avatar"), for: .normal)
//        uibutton.imageEdgeInsets = UIEdgeInsetsMake(-10, -10, -10, -10)
        view.addSubview(uibutton)
//        uibutton.sizeToFit()
        
        let button = Button()
        button.layer.borderWidth = 1
        button.layer.borderColor = UIColor.black.cgColor
        
        button.frame = CGRect(x: 0, y: 350, width: view.bounds.width, height: 40)
        button.setTitle("github.com/coderZsq")
        button.setTitleColor(.red)
//        button.setTitleEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
//        button.setImage(UIImage(named: "avatar") ?? UIImage());
        button.setBackgroundImage(UIImage(named: "avatar") ?? UIImage())
//        button.setImageEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
        view.addSubview(button)
//        button.sizeToFit()
複製程式碼

setTitle && setTitleColor && setBackgroundImage && sizeToFit

        let uibutton = UIButton()
        uibutton.layer.borderWidth = 1
        uibutton.layer.borderColor = UIColor.black.cgColor
        
        uibutton.frame = CGRect(x: 0, y: 100, width: view.bounds.width, height: 40)
        uibutton.setTitle("github.com/coderZsq", for: .normal)
        uibutton.setTitleColor(.red, for: .normal)
//        uibutton.titleEdgeInsets = UIEdgeInsetsMake(0, 0, 0, 0)
//        uibutton.setImage(UIImage(named: "avatar"), for: .normal)
        uibutton.setBackgroundImage(UIImage(named: "avatar"), for: .normal)
//        uibutton.imageEdgeInsets = UIEdgeInsetsMake(-10, -10, -10, -10)
        view.addSubview(uibutton)
        uibutton.sizeToFit()
        
        let button = Button()
        button.layer.borderWidth = 1
        button.layer.borderColor = UIColor.black.cgColor
        
        button.frame = CGRect(x: 0, y: 350, width: view.bounds.width, height: 40)
        button.setTitle("github.com/coderZsq")
        button.setTitleColor(.red)
//        button.setTitleEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
//        button.setImage(UIImage(named: "avatar") ?? UIImage());
        button.setBackgroundImage(UIImage(named: "avatar") ?? UIImage())
//        button.setImageEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
        view.addSubview(button)
        button.sizeToFit()
複製程式碼

setTitle && setTitleColor && setImage && setBackgroundImage

        let uibutton = UIButton()
        uibutton.layer.borderWidth = 1
        uibutton.layer.borderColor = UIColor.black.cgColor
        
        uibutton.frame = CGRect(x: 0, y: 100, width: view.bounds.width, height: 40)
        uibutton.setTitle("github.com/coderZsq", for: .normal)
        uibutton.setTitleColor(.red, for: .normal)
//        uibutton.titleEdgeInsets = UIEdgeInsetsMake(0, 0, 0, 0)
        uibutton.setImage(UIImage(named: "avatar"), for: .normal)
        uibutton.setBackgroundImage(UIImage(named: "avatar"), for: .normal)
//        uibutton.imageEdgeInsets = UIEdgeInsetsMake(-10, -10, -10, -10)
        view.addSubview(uibutton)
//        uibutton.sizeToFit()
        
        let button = Button()
        button.layer.borderWidth = 1
        button.layer.borderColor = UIColor.black.cgColor
        
        button.frame = CGRect(x: 0, y: 350, width: view.bounds.width, height: 40)
        button.setTitle("github.com/coderZsq")
        button.setTitleColor(.red)
//        button.setTitleEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
        button.setImage(UIImage(named: "avatar") ?? UIImage());
        button.setBackgroundImage(UIImage(named: "avatar") ?? UIImage())
//        button.setImageEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
        view.addSubview(button)
//        button.sizeToFit()
複製程式碼

setTitle && setTitleColor && setImage && setBackgroundImage && sizeToFit

        let uibutton = UIButton()
        uibutton.layer.borderWidth = 1
        uibutton.layer.borderColor = UIColor.black.cgColor
        
        uibutton.frame = CGRect(x: 0, y: 100, width: view.bounds.width, height: 40)
        uibutton.setTitle("github.com/coderZsq", for: .normal)
        uibutton.setTitleColor(.red, for: .normal)
//        uibutton.titleEdgeInsets = UIEdgeInsetsMake(0, 0, 0, 0)
        uibutton.setImage(UIImage(named: "avatar"), for: .normal)
        uibutton.setBackgroundImage(UIImage(named: "avatar"), for: .normal)
//        uibutton.imageEdgeInsets = UIEdgeInsetsMake(-10, -10, -10, -10)
        view.addSubview(uibutton)
        uibutton.sizeToFit()
        
        let button = Button()
        button.layer.borderWidth = 1
        button.layer.borderColor = UIColor.black.cgColor
        
        button.frame = CGRect(x: 0, y: 350, width: view.bounds.width, height: 40)
        button.setTitle("github.com/coderZsq")
        button.setTitleColor(.red)
//        button.setTitleEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
        button.setImage(UIImage(named: "avatar") ?? UIImage());
        button.setBackgroundImage(UIImage(named: "avatar") ?? UIImage())
//        button.setImageEdgeInsets(UIEdgeInsetsMake(0, 0, 0, 0))
        view.addSubview(button)
        button.sizeToFit()
複製程式碼

這道題還沒有實現的就是AutoLayout和EdgeInsets, 還有就是在sizeToFit算的最佳尺寸和系統的最佳尺寸有細微出入, 還有就是UIImageView和UILabel的先後載入的問題.

update

    lazy var titleLabel: UILabel =  {
        let titleLabel = UILabel()
        titleLabel.font = UIFont.systemFont(ofSize: 18)
        titleLabel.textAlignment = .center
        return titleLabel
    }()
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對於在sizeToFit算的最佳尺寸和系統的最佳尺寸有細微出入 這個問題是UILabel的預設系統字型大小是17, 而UIButton中的titleLabel的字型大小是18.

    internal func setImage(_ image: UIImage) {
        if !imageViewIsCreated {
            addSubview(imageView)
            if titleLabelIsCreated {
                insertSubview(imageView, belowSubview: titleLabel)
            }
            imageViewIsCreated = true
        }
        imageView.image = image
    }
複製程式碼

對於UIImageView和UILabel的先後載入的問題, 需要在setImage時判斷titleLabel是否存在即可

現已達到完全相同, 接下來就是要解決AutoLayout和EdgeInsets的問題.

update2

通過 nib 進行建立.. 謝謝@夢痕_Lee提供的思路.

實現方法:

1.判斷是否是從nib中建立

    var createdFromNib = false
    
    override init(frame: CGRect) {
        super.init(frame: frame)
    }
    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        createdFromNib = true
    }
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2.重寫系統實現函式intrinsicContentSize並返回最佳尺寸

    override var intrinsicContentSize: CGSize {
        return bestSize()
    }
    
    func bestSize() -> CGSize {
        if titleLabelIsCreated && !imageViewIsCreated && !backgroundImageViewCreated {
            let text: NSString? = titleLabel.text as NSString?
            let titleLabelW: CGFloat = text?.boundingRect(with: CGSize(width: CGFloat(MAXFLOAT), height: bounds.height), options: NSStringDrawingOptions.usesLineFragmentOrigin, attributes: [NSAttributedStringKey.font : titleLabel.font], context: nil).size.width ?? 0.0
            let titleLabelH: CGFloat = text?.boundingRect(with: CGSize(width: titleLabelW, height: CGFloat(MAXFLOAT)), options: NSStringDrawingOptions.usesLineFragmentOrigin, attributes: [NSAttributedStringKey.font : titleLabel.font], context: nil).size.height ?? 0.0
            return CGSize(width: titleLabelW, height: titleLabelH + 10)
        } else if !titleLabelIsCreated && imageViewIsCreated {
            return imageView.image?.size ?? CGSize.zero
        } else if titleLabelIsCreated && imageViewIsCreated {
            let text: NSString? = titleLabel.text as NSString?
            let titleLabelW: CGFloat = text?.boundingRect(with: CGSize(width: CGFloat(MAXFLOAT), height: bounds.height), options: NSStringDrawingOptions.usesLineFragmentOrigin, attributes: [NSAttributedStringKey.font : titleLabel.font], context: nil).size.width ?? 0.0
            let titleLabelH: CGFloat = text?.boundingRect(with: CGSize(width: titleLabelW, height: CGFloat(MAXFLOAT)), options: NSStringDrawingOptions.usesLineFragmentOrigin, attributes: [NSAttributedStringKey.font : titleLabel.font], context: nil).size.height ?? 0.0
            let imageViewW: CGFloat = imageView.image?.size.width ?? 0.0
            let imageViewH: CGFloat = imageView.image?.size.height ?? 0.0
            return CGSize(width: titleLabelW + imageViewW, height: imageViewH > titleLabelH ? imageViewH : titleLabelH)
        } else {
            return backgroundImageView.image?.size ?? CGSize.zero
        }
    }
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3.佈局時判斷即可

    override func layoutSubviews() {
        super.layoutSubviews()

        if createdFromNib {
            frame.size = intrinsicContentSize
        }
        ...
   }
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4.測試一下, 不加sizetofit

        nib_button.layer.borderWidth = 1
        nib_button.layer.borderColor = UIColor.black.cgColor
        
        nib_button.setTitle("github.com/coderZsq")
        nib_button.setTitleColor(.red)
//        nib_button.setTitleEdgeInsets(.zero)
        nib_button.setImage(UIImage(named: "avatar") ?? UIImage())
//        nib_button.setBackgroundImage(UIImage(named: "avatar") ?? UIImage())
        nib_button.setImageEdgeInsets(.zero)
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一樣的完美, 攻克了AutoLayout, 接下來就是EdgeInsets啦~~~

update3

一直理解錯了, intrinsicContentSize這個方法是在新增約束後生效, 不管是nib還是手動約束, 都會生效.

所以update2中只需實現第二步即可, 並不需要其他的判斷.

面試題4 網路架構實現

這道題真是戳中我的軟肋, 網路與多執行緒是我最為薄弱的地方, 現在對執行緒的理解應該已經不錯了, 但是網路還是有所欠缺的, 所以, 我會在今後學習Linux和精讀AFNetWorking && SDWebImage後, 自己寫一個網路架構來進行自我提升.

面試總結

對於兩道演算法題, 我沒有什麼太多想講的, 技不如人吧, 可是演算法題這種東西在iOS上用處其實不是很大, 我就不信那些沒有刷過演算法題的同學, 面對一道從沒有見過的演算法題能夠一下子從容的寫出最優解的. 還有就是UI的那道題目, 坑吧, 誰會去放著好好的現成的不用, 去噁心自己, 還一定要一樣... 我都問過面試官好幾遍, 到底想要做什麼功能... 回答只有, 我不在乎你怎麼寫, 只要和系統的一樣就好了.... 產品附體了麼....

好吧... 技不如人, 被掛了也是理所當然... 不會找什麼藉口... 聽美團的朋友說, 現在只招技術專家, 其他低職級的名額緊縮都不招了... 誒... 隨緣吧...

最後本文中所有的原始碼都可以在github上找到: