在 Angular 5 http 请求中使用 observable 有什么好处? [英] What is the benefit of using observable in Angular 5 http requests?

问题描述

我对在 angular 5 中使用 httpclient 感到困惑.我是 angular 的新手，只是按照官方的 angular 教程进行操作.我对 observables、promise、pipe 等不太了解.目前我正在提供处理所有 http 的服务方法.对于发布请求，我使用管道.下面是方法.

I am confused about using httpclient in angular 5.I am new to angular and just following the official angular tutorial.I dont know much about observables,promise,pipe etc..Currently I am having a service for handling all the http methods.For post request I am using with pipe.Below is the method.

create(model: any,URI) :Observable<Object>{
    return this.http.post(API_URL+URI, model)
    .pipe(
        catchError(this.handleError('create', model))
    );
}



private handleError<T> (operation = 'operation', result?: T) {
        return (error: any): Observable<T> => {

        console.error("default"+error); // log to console instead
        var errors=error["error"];

        var type=errors.errors;

        this.log(`${operation} failed: ${JSON.stringify(errors.errors)}`);

        return of(result as T);
        };
    }

      private log(message: string) {
        this.messageService.add('DataService: ' + message);
      }

在组件内部，我像这样调用这个创建方法..

And inside the component I am calling this create method like this..

onSubmit() { 
        this.loading = true;
        this._dataService.create(this.model,companytype_url).subscribe(data => {
            console.log("inside component data type-company"+JSON.stringify(data));
        },
        error=>{
            var error_data=JSON.stringify(error);
            console.log("inside component error type-company ->" + error_data)
        }
        );
        this.submitted = true;
        this.loading = false;
        this.companytypeForm.reset();
    }

我应该在组件中使用订阅吗?我需要一个通用的 http 类来处理所有的 api 请求.它是一个很大的应用程序，有很多组件.由于我是 Angular 的新手，我对调用 http 方法的不同方式感到困惑.

Should I use subscribe in component? I need a general http class to handle the all the api requests.It is a big application and there are a lot of components.Since I am new to Angular I am confused about the different ways of calling http methods.

推荐答案

我应该在组件中使用订阅吗?

Should I use subscribe in component?

是的.如果您不订阅，则不会向服务器发送任何内容

Yes. If you don't subscribe, nothing will be sent to the server

我需要一个通用的 http 类来处理所有的 api 请求

I need a general http class to handle the all the api requests

这就是HttpClient.如果您的服务是完全通用的，它不会向 HttpClient 已经提供的内容添加任何内容.使用专用服务，它实际上提供了更高级别的抽象:具有类型化参数、必要的转换输入、使用适当的 URL、返回类型化对象、知道如何转换响应等.

That's what HttpClient is. If your service is completely generic, it won't add anything to what HttpClient already provides. Use dedicated services, which actually provide a higher-level abstraction: have typed arguments, transform inputs necessary, use the appropriate URL, return typed objects, know how to transform the response, etc.

由于我是 Angular 的新手，所以我对调用 http 方法的不同方式感到困惑.

Since I am new to Angular I am confused about the different ways of calling http methods.

这就是 Angular 提供...文档的原因.例如，这个 HttpClient 指南，以及这个 RxJS 指南.阅读它们.

That's why Angular provides... documentation. For example, this HttpClient guide, and this RxJS guide. Read them.

这篇关于在 Angular 5 http 请求中使用 observable 有什么好处?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！