Golang中map的三種宣告方式和簡單實現增刪改查

OldBoy~發表於2018-09-13
Golang
package main

import (
    "fmt"
)

func main() {
    test3 := map[string]string{
        "one":   "php",
        "two":   "golang",
        "three": "java",
    }
    no_exsits, ok := test3["three"]
    fmt.Println(no_exsits, ok)
    if no_exsits, ok := test3["four"]; ok {
        fmt.Println(no_exsits)
    } else {
        fmt.Println("KEY not exist")
    }

}

//java true
//KEY not exist

map就相當於php語言中的關聯陣列

//程式碼
package main
import (
    "fmt"
)

func main() {
    //第一種宣告
    var test1 map[string]string
    //在使用map前，需要先make，make的作用就是給map分配資料空間
    test1 = make(map[string]string, 10) 
    test1["one"] = "php"
    test1["two"] = "golang"
    test1["three"] = "java"
    fmt.Println(test1) //map[two:golang three:java one:php]


    //第二種宣告
    test2 := make(map[string]string)
    test2["one"] = "php"
    test2["two"] = "golang"
    test2["three"] = "java"
    fmt.Println(test2) //map[one:php two:golang three:java]

    //第三種宣告
    test3 := map[string]string{
        "one" : "php",
        "two" : "golang",
        "three" : "java",
    }
    fmt.Println(test3) //map[one:php two:golang three:java]


    
    language := make(map[string]map[string]string)
    language["php"] = make(map[string]string, 2)
    language["php"]["id"] = "1"
    language["php"]["desc"] = "php是世界上最美的語言"
    language["golang"] = make(map[string]string, 2)
    language["golang"]["id"] = "2"
    language["golang"]["desc"] = "golang抗併發非常good"
    
    fmt.Println(language) //map[php:map[id:1 desc:php是世界上最美的語言] golang:map[id:2 desc:golang抗併發非常good]]


    //增刪改查
    // val, key := language["php"]  //查詢是否有php這個子元素
    // if key {
    //     fmt.Printf("%v", val)
    // } else {
    //     fmt.Printf("no");
    // }

    //language["php"]["id"] = "3" //修改了php子元素的id值
    //language["php"]["nickname"] = "啪啪啪" //增加php元素裡的nickname值
    //delete(language, "php")  //刪除了php子元素
    fmt.Println(language)
}

 補充：判斷一個不存在的key

package main

import (
    "fmt"
)

func main() {
    test3 := map[string]string{
        "one":   "php",
        "two":   "golang",
        "three": "java",
    }
    no_exsits, ok := test3["three"]
    fmt.Println(no_exsits, ok)
    if no_exsits, ok := test3["four"]; ok {
        fmt.Println(no_exsits)
    } else {
        fmt.Println("KEY not exist")
    }

}
//java true
//KEY not exist

 

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