如何在 Typescript 的回调函数中访问“this”？
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How to access 'this' inside a callback function in Typescript?
提问by Tristan C
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.
一旦调用回调，我试图将在类开头声明的变量（布尔值）设置为 true，但我不断收到 TypeScript 错误。
Here is the error:
这是错误：
TypeError: Cannot set property 'nonReceived' of undefined
Here is my code:
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);
}
});
}
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.
brintree-setup 连接到 Braintree Payments，并等待用户付款信息。他们提交表单后，我需要将变量“this.nonReceived”设置为 true。
回答by Konstantin Vitkovsky
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.
如果您使用 ES5 语法，您可以使用function(){}.bind(this)上下文绑定回调，但使用 Typescript，您可以使用 ES6 语法并使用(parameters) => {function_body}隐式绑定当前上下文的箭头函数。
