类内对象内的函数

Question

我有一个类，这个类有一个函数。 我想从该类的对象内部的另一个函数内部调用该函数。

代码如下：

class Animal
{
    constructor(name)
    {
        this.name = name
    }

    //This is the function i want to call from inside the object below
    emitSound(sound)
    {
        return `I am ${sound}`
    }

    //This is the object with functions
    actions = {
        eat()
        {
            return this.emitSound('eating');
        },
        sleep()
        {
            return this.emitSound('sleeping');
        }
    }
}

const animal = new Animal('Dog');

console.log(animal.actions.eat());

（此代码只是一个示例，我正在开发的应用程序是方式 更复杂）

你怎么看，它返回一个错误，说“this.emitSound()”是undefined。 它的发生是因为函数 eat() 试图从操作对象内部调用 this，不是吗？

所以我需要一种在 actions 对象 函数中调用emitSound() 函数的方法。请帮忙！！！

Answer 1

那是因为 this 引用了 actions，因为您将其称为 actions: actions.eat() 的方法。

一种解决方法是将bind 函数添加到constructor 中的当前实例：

class Animal
{
    constructor(name)
    {
        this.name = name
        this.actions.eat = this.actions.eat.bind(this);
        this.actions.sleep = this.actions.sleep.bind(this);
    }

    //This is the function i want to call from inside the object below
    emitSound(sound)
    {
        return `I am ${sound}`
    }

    //This is the object with functions
    actions = {
        eat()
        {
            return this.emitSound('eating');
        },
        sleep()
        {
            return this.emitSound('sleeping');
        }
    }
}

const animal = new Animal('Dog');

console.log(animal.actions.eat());

其他选项：将函数声明为arrow functions：

class Animal
{
    constructor(name)
    {
        this.name = name
    }

    //This is the function i want to call from inside the object below
    emitSound(sound)
    {
        return `I am ${sound}`
    }

    //This is the object with functions
    actions = {
        eat: () => this.emitSound('eating'),
        sleep: () => this.emitSound('sleeping')
    }
}

const animal = new Animal('Dog');

console.log(animal.actions.eat());