如何从 fetch API 返回 json 响应

问题描述

我有这样的功能:

check_auth(){
    fetch(Urls.check_auth(), {
      credentials: 'include',
      method: 'GET'
    }).then(response => {
      if(response.ok) return response.json();
    }).then(json => {
      return json.user_logged_in;
    });
  }

然后我尝试这样做:

if(this.check_auth()){
    // do stuff
} else {
    // do other stuff
}

但是，this.check_auth() 总是 undefined.

我在这里缺少什么?我认为在 fetch 的 then() 中是 resolved Promise 对象的位置，因此我认为当用户登录时我会得到 true在.但事实并非如此.

What am I missing here? I thought that within fetch's then() was where the resolved Promise object was therefore I thought that I'd get true when the user was logged in. But this is not the case.

任何帮助将不胜感激.

推荐答案

使用回调

check_auth(callback){
    fetch(Urls.check_auth(), {
      credentials: 'include',
      method: 'GET'
    }).then(response => {
      if(response.ok) return response.json();
    }).then(json => {
      callback(json.user_logged_in);
    });
  }

 check_auth(function(data) {
        //processing the data
        console.log(d);
    });

在 React 中它应该更容易处理，您可以调用 fetch 并更新状态，因为每次使用 setState 更新状态时都会调用渲染方法，您可以使用状态进行渲染

In React it should be easier to handle, You can call a fetch and update the state, since on every update of state using setState the render method is called you can use the state to render

check_auth = () =>{
    fetch(Urls.check_auth(), {
      credentials: 'include',
      method: 'GET'
    }).then(response => {
      if(response.ok) return response.json();
    }).then(json => {
         this.setState({Result: json.user_logged_in});
    });
  }

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