我正在从官方文档中学习 Kotlin，我创建了一个 class，如下所示，我创建了一个 constructor，它有两个 参数。 constructor 的主体在 init block 中。

class Person(name: String, surname: String) {
    init {
        Log.d("App", "Hello");
    }
}

好吧，我想再创建一个 constructor，它将在 constructor 中使用一个 parameter。 Kotlin

最佳答案

init 不是构造函数的主体。它在主构造函数之后调用，带有主构造函数的上下文。

在官方文档中给出:

The primary constructor cannot contain any code. Initialization code can be placed in initializer blocks, which are prefixed with the init keyword:

class Customer(name: String) {
    init {
        logger.info("Customer initialized with value ${name}")
    }
}

Note that parameters of the primary constructor can be used in the initializer blocks. They can also be used in property initializers declared in the class body:

class Customer(name: String) {
    val customerKey = name.toUpperCase()
}

In fact, for declaring properties and initializing them from the primary constructor, Kotlin has a concise syntax:

class Person(val firstName: String, val lastName: String, var age: Int) {
    // ...
}

根据您的问题，您可以添加一个构造函数来接受一个参数，如下所示:

class Person(name: String, surname: String) {

    constructor(name: String) : this(name, "") {
        // constructor body
    }

    init {
        Log.d("App", "Hello");
    }
}

但它看起来不正确，因为我们没有必要传递第二个参数空字符串。所以我们可以像下面这样订购构造函数:

class Person(name: String) {

    constructor(name: String, surname: String) : this(name) {
        // constructor body
    }

    init {
        Log.d("App", "Hello");
    }
}

希望对你有帮助。

https://stackoverflow.com/questions/44276277/