Angular 2订阅不工作

Question

我收到异常'不能读取属性'订阅'的undefined'，但我没有得到它，我做错了什么。

checkUserCredentials() { 
    let response; 
    let user = {email: this.email, password: this.password}; 
    this.userService.getUser(user).subscribe((res) => response = res); 
    } 

服务：

getUser(user): any { 
    //this.http.get('http://localhost:3000/users?email = '+user.email+'&password='+user.password, 
    let headers = new Headers(); 
    let postResponse; 
    headers.append('Content-Type', 'application/json'); 
    this.http.post('http://localhost:3000/users', 
     JSON.stringify(user), 
     {headers:headers}) 
     .map((res: Response) => res.json()) 
    } 

Answer 1

您需要将getUser方法中返回：

getUser(user): any { 
    let headers = new Headers(); 
    let postResponse; 
    headers.append('Content-Type', 'application/json'); 
    return this.http.post('http://localhost:3000/users', 
    JSON.stringify(user), 
    {headers:headers}) 
    .map((res: Response) => res.json()) 
} 

Answer 2

有一个return失踪。该方法不返回任何内容，为此它含蓄地返回undefined这会导致错误您将获得：

getUser(user): any { 
    //this.http.get('http://localhost:3000/users?email = '+user.email+'&password='+user.password, 
    let headers = new Headers(); 
    let postResponse; 
    headers.append('Content-Type', 'application/json'); 
    // vvv missing return 
    return this.http.post('http://localhost:3000/users', 
     JSON.stringify(user), 
     {headers:headers}) 
     .map((res: Response) => res.json()) 
    }