为什么当我通过中间函数管道我的方法定义时，胖箭头不绑定到这？ [英] Why doesn't the fat arrow bind to this when I pipe my method definition thru an intermediary function?

问题描述

我有以下代码，声明一个方法，在函数结果分配给原型槽之前由中介
函数建议。

I have the following code that declares a method which is advised by an intermediary function before the function result is assigned to a prototype slot.

class A
    somemethod: advise => @dosomething()

为什么胖箭头在这种情况下不绑定到实例？ p>

Why does the fat arrow does not bind to the instance in this case?

推荐答案

简单回答

和函数
定义破坏了使CS在构造函数中发出
绑定代码的语法模式。

Simple answer

When an intermediary is put between the prototype slot name and function definition you break the syntactic pattern that makes the CS emit the binding code in the constructor

class A
    foo: (paramlist) =>
    bar: ()=>
    baz: =>

所有这些方法定义在生成的Javascript构造函数中发出此代码

all these method definitions emit this code in the generated Javascript constructor

function A() {
    this.foo = __bind(this.foo, this);
    this.bar = __bind(this.bar, this);
    this.baz = __bind(this.baz, this);
}

如果你把东西放在你之间打破了语法模式$ b Coffeescript编译器可以识别该模式并生成必要的代码。

If you put something in between you break that syntactic pattern by which the Coffeescript compiler can recognize that pattern and generated the necessary code.

class A
    helpWhereIsMyMethod: processTheFollowing => @doSomething()

在这种情况下，不会生成构造函数中的绑定调用

In this case no bind calls in the constructor are generated

当你定义一个原型槽（名称）并立即分配一个（匿名）函数
您已经有效地创建了一个句柄，您可以稍后访问该函数
并处理它或调用它（大多数情况下）。

When you define a prototype slot (name) and immediately assign a (anonymous) function to it you have effectively created a handle by which you can later access that function and "process" it or call it (most of the cases).

管道你的函数到另一个函数（中介）在绑定结果
到一个原型槽之前你创建一个匿名函数，你不能访问以后。

If you pipe your function into another function (the intermediary) before binding the result to a prototype slot you create effectively an anonymous function that you can't access later.

因此Coffeescript编译器不知道如何在构造函数
中发出绑定代码，因为在对象创建期间，不授予对匿名函数的访问

So the Coffeescript compiler doesn't know how to emit the bind code in the constructor because during object creation time the access to the anonymous function is not given anymore.

中介函数也可以生成自己的代码并发出这个新的代码绑定到原型槽。

Also the intermediary function could generate code of its own and emit this new code to be bound to the prototype slot.

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