角2：如何調用一個函數得到響應後訂閱http.post

Question

我需要調用一個方法後，從HTTP POST請求獲取數據

服務：request.service.TS

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

     }, error => { 
    } 
); 

} 

組件：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(); 
} 

只有當我改變工作：

服務：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 => { 
    } 
); 

} 

但我需要調用this.get_categories(1);後要調用的方法send_catagories()構件的內部這樣

組件：categories.TS

search_categories() { 

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

我做錯了什麼？

Answer 1

更新您的get_categories()方法到返回總（包裹在一個可觀察）：

// 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()，您可以訂閱可觀察到的由get_categories()返回（或者你可以繼續通過鏈接多個RxJS運營商轉換它）：

// 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") 
    ); 
} 

注那你只訂閱ONCE，最後。

就像我在評論中說，任何可觀察到的.subscribe()方法接受3次回調是這樣的：

obs.subscribe(
    nextCallback, 
    errorCallback, 
    completeCallback 
); 

他們必須按以下順序進行傳遞。你不必通過這三個。很多時候，只有nextCallback實現：

obs.subscribe(nextCallback); 

Answer 2

您可以將回調函數添加到您的get_category（...）參數列表中。

例：

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

     }, error => { 
    } 
); 

} 

然後你只需調用get_category（...）這樣的：

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(); 
);  
} 

然後

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

Answer 4

可以作爲一個lambda表達式作爲第三個參數（上完成）碼的訂閱方法。在這裏我重新設置departmentModel變量爲默認值。

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