javascript - 将其绑定(bind)到回调函数

Question

如何使用 call 或 apply 将其绑定(bind)到回调函数？

    beforeModel: function(params){

        return this.get('session').authenticate().then(function(){
            this.findClient(params);
        }.bind(this)).catch(function(err){
          //retrieve new session
          return this.get('session').authorize().then(function(){
            this.findClient(params);
          }.call(this));
        });
    },

在某个时刻抛出错误:

类型错误:this.get 不是函数

这应该指的是 Ember Controller 范围，为什么如果我先用 bind(this) 绑定(bind)，然后 call(this) 会抛出错误？

Answer 1

为此，您最好使用bind。

function doSomething(){
    return authorize().then((function(){

       }).bind(this));
}

The bind() function creates a new function (a bound function) with the same function body (internal call property in ECMAScript 5 terms) as the function it is being called on (the bound function's target function) with the this value bound to the first argument of bind(), which cannot be overridden.

MDN

编辑:你仍然犯同样的错误。 Promise 方法 then 接受一个函数引用，因此一旦确定就可以调用它。您要做的就是执行函数并将函数的返回值传递给 then 方法，在本例中是另一个 Promise 对象。

让我们分解一下:

beforeModel: function(params) {
  //Function to be passed down to your promise to find a Client.
  //Note that nothing gets passed down to the next step once the promise gets settled.
  var fClient = function() {
    this.findClient(params);
  };
  //We want this to be this (of beforeModel function).
  fClient = fClient.bind(this);

  //I have no idea what you are trying to do with the catch...
  var reAttachPromise = function() {
    return this.get('session').authorize().then(fClient);
  };
  //We want this to be this (of beforeModel function).
  reAttachPromise = reAttachPromise.bind(this);

  return this.get('session').authenticate().then(fClient).catch(reAttachPromise);
  //can be reduced to:
  // return reAttachPromise().catch(reAttachPromise);
}