Kotlin - 了解吸气剂和二传手

Question

Kotlin自动生成它的吸气剂和设置,但我从不参考它们？另外,在Kotlin中编写自定义getter/setter的正确方法是什么？当我说myObj.myVar = 99我觉得我是直接访问myVar的公共领域myObj？这里到底发生了什么？

Answer 1

这已经在一些地方得到了回答,但我想我会分享一个具体的例子,让人们从Java/C#/ C/C++过渡到Kotlin,并且我遇到了同样的问题:

我很难理解getterter和setter在Kotlin中是如何工作的,特别是因为它们从未被明确调用过(因为它们是在Java中).因此,我感到不舒服,因为我们只是直接将vars/vals称为字段.所以我做了一个小实验来证明事实并非如此,事实上,当你访问变量/值时,它是在Kotlin中调用的隐式(自动生成的)或显式的getter/setter.不同的是,您没有明确要求默认的getter/setter.

从文档中 - 声明属性的完整语法是:

var <propertyName>: <PropertyType> [= <property_initializer>]
   [<getter>]
   [<setter>]

我的榜样是

class modifiersEg {

/** this will not compile unless:
 *      - we assign a default here
 *      - init it in the (or all, if multiple) constructor
 *      - insert the lateinit keyword    */
var someNum: Int?
var someStr0: String = "hello"
var someStr1: String = "hello"
    get() = field  // field is actually this.someStr1, and 'this' is your class/obj instance
    set(value) { field = value }

// kotlin actually creates the same setters and getters for someStr0
// as we explicitly created for someStr1

var someStr2: String? = "inital val"
    set(value) { field = "ignore you" }

var someStr3: String = "inital val"
    get() = "you'll never know what this var actually contains"

init {
    someNum = 0

    println(someStr2) // should print "inital val"

    someStr2 = "blah blah blah"
    println(someStr2) // should print "ignore you"

    println(someStr3) // should print "you'll never know what this var actually contains"
}

我希望这对其他人有帮助吗？