角2：如何调用一个函数得到响应后订阅http.post

Question

我需要调用一个方法后，从HTTP POST请求获取数据

服务：request.service.TS

get_categories(number){ 
this.http.post(url, body, {headers: headers, withCredentials:true}) 
    .subscribe( 
     response => { 
     this.total = response.json(); 

     }, error => { 
    } 
); 

} 

组件：categories.TS

search_categories() { 

this.get_categories(1); 
//I need to call a Method here after get the data from response.json() !! e.g.: send_catagories(); 
} 

只有当我改变工作：

服务：request.service.TS

get_categories(number){ 
this.http.post(url, body, {headers: headers, withCredentials:true}) 
    .subscribe( 
     response => { 
     this.total = response.json(); 
     this.send_catagories(); //here works fine 

     }, error => { 
    } 
); 

} 

但我需要调用this.get_categories(1);后要调用的方法send_catagories()构件的内部这样

组件：categories.TS

search_categories() { 

this.get_categories(1); 
this.send_catagories(response); 
} 

我做错了什么？

Answer 1

更新您的get_categories()方法到返回总（包裹在一个可观察）：

// Note that .subscribe() is gone and I've added a return. 
get_categories(number) { 
    return this.http.post(url, body, {headers: headers, withCredentials:true}) 
    .map(response => response.json()); 
} 

在search_categories()，您可以订阅可观察到的由get_categories()返回（或者你可以继续通过链接多个RxJS运营商转换它）：

// send_categories() is now called after get_categories(). 
search_categories() { 
    this.get_categories(1) 
    // The .subscribe() method accepts 3 callbacks 
    .subscribe(
     // The 1st callback handles the data emitted by the observable. 
     // In your case, it's the JSON data extracted from the response. 
     // That's where you'll find your total property. 
     (jsonData) => { 
     this.send_categories(jsonData.total); 
     }, 
     // The 2nd callback handles errors. 
     (err) => console.error(err), 
     // The 3rd callback handles the "complete" event. 
    () => console.log("observable complete") 
    ); 
} 

注那你只订阅ONCE，最后。

就像我在评论中说，任何可观察到的.subscribe()方法接受3次回调是这样的：

obs.subscribe(
    nextCallback, 
    errorCallback, 
    completeCallback 
); 

他们必须按以下顺序进行传递。你不必通过这三个。很多时候，只有nextCallback实现：

obs.subscribe(nextCallback); 

Answer 2

您可以将回调函数添加到您的get_category（...）参数列表中。

例：

get_categories(number, callback){ 
this.http.post(url, body, {headers: headers, withCredentials:true}) 
    .subscribe( 
     response => { 
     this.total = response.json(); 
     callback(); 

     }, error => { 
    } 
); 

} 

然后你只需调用get_category（...）这样的：

this.get_category(1, name_of_function); 

Answer 3

get_categories(number){ 
return this.http.post(url, body, {headers: headers, withCredentials:true}) 
     .map(t=> { 
      this.total = t.json(); 
      return total; 
     }).share(); 
);  
} 

然后

this.get_category(1).subscribe(t=> { 
     this.callfunc(); 
}); 

Answer 4

可以作为一个lambda表达式作为第三个参数（上完成）码的订阅方法。在这里我重新设置departmentModel变量为默认值。

saveData(data:DepartmentModel){ 
    return this.ds.sendDepartmentOnSubmit(data). 
    subscribe(response=>this.status=response, 
    ()=>{}, 
    ()=>this.departmentModel={DepartmentId:0}); 
}