Kotlin中apply和let的区别

Posted 2022-08-16 zhangjin1120

目录

• apply的用法
• let的用法

apply的用法

class Student 
    var name: String? = null
    var age: Int? = null


fun main() 
    var s = Student().apply 
        name = "zhangjin"
        age = 20
    
    println(s.name + " " + s.age)

输出结果如下：

let的用法

class Student 
    var name: String? = null
    var age: Int? = null



fun main() 
    var s = Student().let 
        it.name = "zhangjin"
        it.age = 20
    
    println(s)

    var s2 = Student().let 
        it.name = "zhangjin"
        it.age = 20
        it.age
    
    println(s2)

    var s3 = Student().let 
        it.name = "zhangjin"
        it.age = 20
        it
    
    println(s3.name)

看下运行效果：

对于Unit不理解的，可以看这篇：Kotlin中的Unit。从运行结果，可以看出let把闭包中最后一行代码的返回值，赋值给var变量。