第七章、Groovy物件導向

往前的娘娘發表於2020-12-02
物件

文章目錄

1、定義類和指令碼

1.1、定義成員變數和本地變數

  • 定義成員變數, 本地變數

  • /**
 * 宣告變數
 * @author liangchen* @date 2020/11/8
 */
class DeclareVariableDemo {

    // 成員變數
    public fieldWithModifier
    String typedField
    def untypeField
    protected field1, field2, field3
    private assignedField = new Date()
    static classField
    public static final String CONSTA = 'a', CONSTB = 'b'

    static void main(String[] args) {
        // ClassCastException 類轉換異常
        final String PI = '3.14'
        assert PI.class.name == 'java.lang.String'

        assert PI.size() == 4

        GroovyAssert.shouldFail(ClassCastException) {
            Float areaofCircleRadiusOne = PI
        }
    }

    def someMethods(){
        // 本地變數
        def localUntypedMethodVar = 1

        int localTypedMethodVar = 1

        def localVarWithoutAssigment , andAnotherOne

    }

    def localvar = 1,boundvar1 = 1
    def someMethod(){
        def localMethodVar = 1
        boundvar2 = 1
    }



}

  • 沒有欄位預設呼叫方法

  • /**
 * 引用成員變數
 * @author liangchen* @date 2020/11/8
 */
class ReferenceFieldDemo {
    static void main(String[] args) {
        def counter = new Counter()
        counter.count = 1
        assert counter.count == 1

        def fieldName = 'sum'
        counter[fieldName] = 2
        assert counter.sum == 2

        // 沒有值，就呼叫get方法
        def pretender = new PretendFieldCounter()
        assert pretender.isNoField == 'pretend value'

        assert pretender.count == 0
        //呼叫set方法 count ==1
        pretender.isNoFieldEither = 'just to increase counter'
        // 呼叫set方法  count==2
        pretender.aaa = 1
        assert pretender.count == 2
    }
}
class Counter{
    public count =0
    public sum = 0
}

class PretendFieldCounter {
    public count = 0

    Object get(String name) {
        return 'pretend value'
    }

    void set(String name, Object value) {
        count++

    }
}

1.2、定義方法和引數

  • 可以是確定型別和不確定型別

  • /**
 * 宣告方法 和入參型別
 * @author liangchen* @date 2020/11/8
 */
class ClassWithTypedAndUntypedMethods {

    static void main(args) {
        def some = new ClassWithTypedAndUntypedMethods()
        some.publicVoidMethod()
        assert 'hi' == some.publicUntypedMethod()
        assert 'ho' == some.publicTypeMethod()
        def classWith = new ClassWithTypedAndUntypedMethodParams()
        // 入參型別
        assert 'untyped' == classWith.method(1)
        assert 'typed' == classWith.method('whatever')
        assert  'two args' == classWith.method(1,2)

    }


    /**
     * 沒有返回值
     */
    void publicVoidMethod(){}

    /**
     * 沒有返回型別方法
     * @return
     */
    def publicUntypedMethod(){
        return 'hi'
    }

    /**
     * 有返回值型別
     * @return
     */
    String publicTypeMethod(){
        return 'ho'
    }
    private static final void combinedMethod(){}
}

class ClassWithTypedAndUntypedMethodParams {
    static void main(args) {

    }

    /**
     * 不確定型別入參
     * @param arg
     * @return
     */
    static method(arg){
        return 'untyped'
    }

    /**
     * 有型別入參
     * @param arg
     * @return
     */
    static method(String arg) {
        return 'typed'
    }

    /**
     * 兩個引數
     * @param arg1
     * @param arg2
     * @return
     */
    static method(arg1, Number arg2) {
        return 'two args'
    }
}

  • map, list 陣列入參

    • /**
 * list map 入參
 * @author liangchen* @date 2020/11/9
 */
class Summer {

    static void main(String[] args) {
        def summer = new Summer();
        assert  2 == summer.sumWithDefualts(1,1)

        assert 3 == summer.sumWithDefualts(1, 1, 1)

        assert 2 == summer.sumWithList([1,1])
        assert 3 == summer.sumWithList([1,1,1])

        assert 2 == summer.sumWithOptionals(1,1)
        assert 3 == summer.sumWithOptionals(1,1,1)

        assert 2 == summer.sumNamed(a:1, b:1)
        assert 3 == summer.sumNamed(a: 1, b: 1, c: 1)
        assert 1 == summer.sumNamed(c:1)

    }

    def sumWithDefualts(a, b, c = 0) {
        return a + b + c

    }

    def sumWithList(List args) {
        return args.inject (0){sum, i -> sum +=i}
    }

    def sumWithOptionals(a, b, Object[] optionals) {
        return a + b + sumWithList(optionals.toList())
    }
/**
 * 入參為map
 * @param args
 * @return
 */

    def sumNamed(Map args) {
        // 不存在設定0
        ['a','b','c'].each {args.get(it, 0)}
        return args.a + args.b + args.c
    }
}

1.3、?. 判斷是否連續為空 （短路運算子）

  • 避免連續判空

    • /**
 * ?. 避免空指標,連續判空
 * @author liangchen* @date 2020/11/9
 */
class ProtectionNPEs {

    static void main(String[] args) {
        def map = [a: [b: [c: 1]]]
        assert  map.a.b.c ==1

        if (map && map.a && map.a.x) {
            assert map.a.x.c == null
        }

        try {
            assert map.a.x.c == null
        } catch (NullPointerException ignore) {

        }
        assert map?.a?.x?.c==null
    }

}

1.4、構造器

  • 指定成員變數名和其他方式

    • /**
 * @author liangchen* @date 2020/11/9
 */
class CallConstructorDemo {
    String name, product

    CallConstructorDemo(name, product) {
        this.name = name
        this.product = product
    }

    // Java 的方式
    def first = new CallConstructorDemo('Canoo', "ULC")

    // as 語法
    def second = ['Canoo','ULC'] as CallConstructorDemo

    // 自己陣列元素
    CallConstructorDemo third = ['Canoo', 'ULC']
}


class CallConstructorNameDemo{
    String name, product

    public static void main(String[] args) {
        // 可以指定成員變數名
        new CallConstructorNameDemo()
        new CallConstructorNameDemo(name: 'Canoo')
        new CallConstructorNameDemo(product:'ULC')
        new CallConstructorNameDemo(name: 'Canoo', product: 'ULC')
        
    }
}

2、組織類和指令碼

2.1、檔案與類關係

  • 一個檔案有多個類

    • /**
 * 一個groovy 有兩個類
 * @author liangchen* @date 2020/11/9
 */
class MultipleClassDemo {
    static void main(String[] args) {
        def canoo = new Vendor()
        canoo.name = 'jack'
        canoo.product='apple'
        canoo.address.street = '天頂鄉'
        canoo.address.zip = 1121
        canoo.address.town = '嶽麓區'
        canoo.address.state = '長沙'
        // 查詢匹配字元
        assert canoo.dump() =~ /apple/
        // 查詢匹配字元
        assert canoo.address.dump() =~/1121/
        println canoo.address.dump()
    }
}
class Vendor {
    public String name
    public String product

    public Address address =new Address();
}
class Address{
    public String  street, town , state
    public int zip
}

2.2、在包組織類

  • 跟java類似

  • 預設匯入語句

    • import java.lang.*

import java.util.*

import java.io.*

import java.net.*

import groovy.lang.*

import groovy.util.*

import java.math.BigInteger

import java.math.BigDecimal

  • 匯入設定別名 ( 避免相同類名，不同包下，識別更快)

    • 需要繼承類

    • package com.jack.groovy.ch7.thirdparty

/**
 * @author liangchen* @date 2020/11/10
 */
class MathLib {

    Integer twice(Integer value) {
        return value * 3

    }

    Integer half(Integer value) {
        return value / 2

    }
}

    • 繼承類

      • package com.jack.groovy.ch7

// 這裡使用 as 為這個匯入設定別名
import com.jack.groovy.ch7.thirdparty.MathLib as TypeMathLib
/**
 * @author liangchen* @date 2020/11/10
 */
class MathLib extends TypeMathLib  {

    /**
     * 訂正 2倍
     * @param value
     * @return
     */
    Integer twice(Integer value) {
        return value * 2

    }

    static void main(String[] args) {
        def mathlib = new MathLib()
        assert 10 == mathlib.twice(5)
        assert  2 == mathlib.half(5)
    }

}

2.3、考慮更深classpath(類路徑)

3、物件導向的高階特性

3.1、使用繼承

  • 類似java

3.2、使用介面

  • 類似java

3.3、多方法（過載）

  • 方法名一樣，入參不一樣

  • /**
 * 方法過載
 * @author liangchen* @date 2020/11/10
 */
class Multimethod {

    def oracle(Object o) {
        return 'object'
    }

    def oracle(String o) {
        return 'string'
    }

    static void main(String[] args) {
       def multi =  new Multimethod()
        Object x =1
        Object y = 'foo'

        assert 'object' == multi.oracle(x)

        assert 'string' == multi.oracle(y)

    }

}

3.4、使用trait

  • trait 關鍵字

  • /**
 * trait 有點類似 介面，只不過他有一些方法和屬性， 應該說是抽象類和介面結合體
 * @author liangchen* @date 2020/11/10
 */
class TraitDemo {

    trait HashId{
        long id
    }

    trait HasVersion{
        long version
    }
    trait Persistent{
        boolean save(){
            println "saving ${this.dump()}"
        }
    }

    trait  Entity implements Persistent ,HashId, HasVersion{
        boolean save(){
            version++
            Persistent.super.save()
        }
    }
    class Publication implements  Entity{
        String title
    }

    class Book extends  Publication{
        String isbn
    }

    static void main(String[] args) {
        Entity gina = new Book(id:1,version: 1,title: 'gina', isbn: "11111")
        gina.save()
        assert gina.version == 2
    }
}

4、GroovyBeans使用

4.1、宣告bean

  • /**
 * groovy bean 定義
 * @author liangchen* @date 2020/11/10
 */
class MyBeanDeom {

    static class MyBean implements Serializable{
        String myprop
				//沒有定義型別
        def untyped
      	//定義型別
        String typed
				
        def item1, item2
				//賦值初始值
        def assigned = 'default value'
    }

    static void main(String[] args) {
      MyBean myBean =  new MyBean()
       assert 'default value' == myBean.getAssigned()
        myBean.setUntyped('some value')
        assert 'some value' == myBean.getUntyped()
        
    }
}

4.2、beans執行特徵

  • 獲取field（成員變數）和方法

    • /**
 * 呼叫groovy方法
 * @author liangchen* @date 2020/11/10
 */
class CallGroovyWayDemo {

   static class MrBean {
        String firstname, lastname
        String getName (){
            return "$firstname $lastname"
        }
    }

     static void main(String[] args) {
         def bean = new MrBean(firstname: 'Rowan')
         bean.lastname = 'Jack'
         // 自動呼叫name --> getName 方法
         assert 'Rowan Jack' == bean.name

         //獲取成員變數，使用.@
         def beanss = new DoublerBean(value: 100)
         assert 200 == beanss.value
         assert 100 == beanss.@value

     }

    /**
     * 獲取成員變數，使用.@
     *
     */

    static  class DoublerBean {
        public value

        void setValue(value) {
            this.value = value
        }

        def getValue() {
            value * 2
        }
    }
}

4.3、在任何類中使用bean 的方法

  • 獲取def 修飾的field 欄位

    • /**
 * 獲取bean的屬性
 * 獲取def 修飾的變數
 * @author liangchen* @date 2020/11/10
 */
class GDKBeanProperties {

    static class ClassWithProperties{
        def someProperty
        public someField
        private somePrivateField
    }

    static void main(String[] args) {
       def obj = new ClassWithProperties()
        def store = []
        obj.properties.each { property ->
            store += property.key
            store += property.value
        }
        assert store.contains('someProperty')
        assert store.contains('someField')  == false
        assert store.contains('somePrivateField') == false
        assert store.contains('class')

        assert obj.properties.size() == 2
    }

}

4.4、Field、accessors、maps and Expando

  • Expando

    • /**
 * 動態擴充套件屬性和方法 Expando
 * @author liangchen* @date 2020/11/10
 */
class ExpandoDemo {

    static void main(String[] args) {
        def boxer = new Expando()
        assert null == boxer.takeThis
        // 賦值 takeThis 不存在的值
        boxer.takeThis = 'jack'
        assert 'jack' == boxer.takeThis
        // 定義方法
        boxer.fightBack = {times -> delegate.takeThis * times}
        assert  'jackjack' == boxer.fightBack(2)
    }
}

5、使用高階語法特性

5.1、使用GPaths查詢物件

  • /**
 *  GPath 解析
 * @author liangchen* @date 2020/11/10
 */
class GPathInvoiceDemo {

    static class Invoice{
        List items
        Date date
    }

    static class LineItem{
        Product product
        int count
        int total(){
            return product.dollar * count
        }
    }

    static class Product {
        String name
        def dollar
    }

    static void main(String[] args) {
        def ulcDate = Date.parse('yyyy-MM-dd', '2015-01-01')
        def otherDate = Date.parse('yyy-MM-dd', '2015-02-02')
        def ulc = new Product(dollar: 1499, name: 'ULC')
        def ve = new Product(dollar: 499, name: 'Visual Editor')

        def invoices = [
                new Invoice(date: ulcDate, items: [
                        new LineItem(count: 5, product: ulc),
                        new LineItem(count: 1, product: ve)
                ]),
                new Invoice(date: otherDate, items: [
                        new LineItem(count: 4, product: ve)
                ])
        ]
        // lineItem 平鋪，拆開
        def allItems = invoices.items.flatten()

        // 迴圈呼叫 total方法
        assert [5*1499, 499, 4*499] == allItems*.total()

        // 查詢 數量大於 7000的
        assert ['ULC'] == allItems.grep{it.total() > 7000}.product.name

        // product == ulc , date日期變成字串
        def searchDates = invoices.grep { it.items.any{it.product == ulc}}.date*.toString()
        assert [ulcDate.toString()] == searchDates
    }
}

5.2、注入*操作

  • /**
 *    * 號操作
 * @author liangchen* @date 2020/11/10
 */
class SpreadDemo {

    def getList(){
        return [1,2,3]
    }

    def sum(a, b, c) {
        return a + b + c
    }

    static void main(String[] args) {
       def spread =  new SpreadDemo()
        // 直接呼叫getList 方法獲取到值作為sum的引數
        assert 6 == spread.sum(*spread.list)

        // 直接使用*變數陣列
        def range = (1..3)
        assert [0,1,2,3] == [0, *range]

        // 或者map 或者map *:map
        def map = [a:1, b:2]
        assert [a:1, b:2, c:3] == [c:3, *:map]
    }

}

5.3、利用命令鏈來使用精確語法

6、總結

  1. 方法、成員變數、區域性變數定義（對比java來說的）
  2. groovybean定義

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