如何在Typescript的回调函数中访问“ this”？ [英] How to access 'this' inside a callback function in Typescript?

问题描述

一旦尝试调用回调，我试图将在类开头（布尔值）声明的变量设置为true，但是我一直收到TypeScript错误。

I am trying to set a variable declared at the beginning of the class (a boolean) to true once a callback is called, but I keep getting a TypeScript erorr.

这是错误：

TypeError: Cannot set property 'nonReceived' of undefined

这是我的代码：

  finalizeToken(){
  braintree.setup(JSON.parse(this.finalToken), 'dropin', {
     container: 'dropin-container',
     defaultFirst: true,
      form: 'checkout-form',
      onPaymentMethodReceived: function (obj) {
        this.nonReceived = true;
      localStorage.setItem('nonce', obj.nonce);
    }
  });  
}

brintree设置连接到Braintree Payments，并等待用户付款信息。他们提交表单后，需要将变量 this.nonReceived设置为true。

The brintree-setup connect to Braintree Payments, and awaits user payment info. Once they submit the form, I need the variable "this.nonReceived" to be set to true.

推荐答案

如果使用ES5您可以使用 function（）{}。bind（this）语法将回调与上下文绑定，但是使用Typescript可以使用ES6语法并使用箭头功能（参数）=> {function_body} 隐式绑定当前上下文。

If you use ES5 syntax you could use function(){}.bind(this) to bind the callback with the context but with Typescript you can use ES6 syntax and use arrow function (parameters) => {function_body} which bind current context implicitly.

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