Angular 5同步HTTP调用 [英] Angular 5 synchronous HTTP call

问题描述

我有一个Angular 5应用程序，在其中我必须调用一些繁重的REST服务(通常需要几秒钟).我在应用程序的不同部分需要它的结果，因此我想将结果存储在DataStorageService中. 基本上，这是我想要实现的:

I have an Angular 5 application in which I have to call some heavy REST service (usually takes some seconds). I need its result in different part of application, so I would like to store the result in a DataStorageService. Basically, this is I would like to achieve:

@Injectable()
export class DataStorageService {

private result: MyCustomObject;

constructor(private service: Service) {}

getResult(): MyCustomObject {
    if (typeof this.result === 'undefined') {
        // save result
    }
    return result;
}

问题是如何等待HTTP请求完成，然后保存并返回结果"对象.我也尝试使用Promise和Observable解决该问题，但是它们都无法正常工作.

The question is how I can wait until HTTP request is finished and then save and return the 'result' object. I tried to solve it using Promise and Observable as well, but none of them worked fine.

1. 可观察的:

1. Observable:

if (typeof this.result === 'undefined') {
    this.service.call()
        .subscribe(response => this.result = response);
}
return this.result;  // wait for save and return MyCustomObject

承诺:

Promise:

if (typeof this.result === 'undefined') {
    this.service.call()
        .toPromise()
        .then(response => this.result = response);
}
return this.result;  // wait for save and return MyCustomObject

推荐答案

尝试使用await/async

async getResult(): Promise<MyCustomObject> {
    if (typeof this.result === 'undefined') 
    {
        // save result
        this.result = await this.service.call()
        .toPromise()
        .then(resp =>resp as MyCustomObject);//Do you own cast here

    }
    return this.result;
}

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