Kotlin数据类

港控/mmm° 2022-05-28 08:38 158阅读 0赞

一、数据类  
再见，Javabean  
默认实现了copy、toString等方法  
componentN方法

二、allOpen和noArg插件  
![这里写图片描述][70]

build.gradle的源码

group 'net.println.kotlin'
    version '1.0-SNAPSHOT'
    
    buildscript {
        ext.kotlin_version = '1.1.0'
    
        repositories {
            mavenCentral()
        }
        dependencies {
            classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
            classpath "org.jetbrains.kotlin:kotlin-noarg:$kotlin_version"
            classpath "org.jetbrains.kotlin:kotlin-allopen:$kotlin_version"
        }
    }
    
    apply plugin: 'java'
    apply plugin: 'kotlin'
    apply plugin: 'kotlin-noarg'
    apply plugin: 'kotlin-allopen'
    
    noArg{
        annotation("net.println.kotlin.chapter4.annotations.PoKo")
    }
    
    allOpen{
        annotation("net.println.kotlin.chapter4.annotations.PoKo")
    }
    
    sourceCompatibility = 1.5
    
    repositories {
        mavenCentral()
    }
    
    dependencies {
        compile "org.jetbrains.kotlin:kotlin-stdlib-jre8:$kotlin_version"
        testCompile group: 'junit', name: 'junit', version: '4.11'
    }

三、来看一个例子

package net.println.kotlin.chapter4.dataclass
    
    import net.println.kotlin.chapter4.annotations.PoKo
    
    /** * @author:wangdong * @description: */
    /**加data后就不用再写toString方法了*/
    @PoKo
    data class Country(val id: Int,val name: String)
    
    
    /** * 自定义一个 */
    class ComponentX{ 
        operator fun component1(): String{
            return "您好，我是"
        }
    
        operator fun component2(): Int{
            return 1
        }
    
        operator fun component3(): Int{
            return 1
        }
    
        operator fun component4(): Int{
            return 0
        }
    }
    
    fun main(args: Array<String>) {
        val china = Country(0,"中国")
        println(china)
        //写法一，component1是默认有的
        //component1对应第一个参数
        println(china.component1())
        //component2对应第二个参数
        println(china.component2())
    
        //写法二
        //下面类似
        val (id,name) = china
        println(id)
        println(name)
    
        //写法三
        for ((index,value) in args.withIndex()){
            println(index)
            println(value)
        }
    
        val componentX = ComponentX()
        val (a,b,c,d) = componentX
        println("$a $b $c $d")
    }

输出结果：

Country(id=0, name=中国)
    0
    中国
    0
    中国
    您好，我是 1 1 0

好了，结束了

[70]: /images/20220528/fe322eba3ef041f99961df6f47b5633b.png