Question

我正在使用打字稿并尝试获取我们目前所处位置的地理位置。我可以获取位置，但我的代码继续而不设置位置。我决定使用await并承诺。我创建了一个看起来像这样的服务：

@Injectable()
export class GoogleMapsService  {

private latitude: number;
private longitude:number;

public currentLongitude(): number {
    return this.longitude;
}
public currentLatitude(): number {
    return this.latitude;
}

constructor() {
    this.setCurrentLocation();
}

private async setCurrentLocation() {
    let location: GoogleLocation = await this.getLocation();

    this.latitude = location.latitude;
    this.longitude = location.longitude;
}


private getLocation(): Promise<GoogleLocation> {
    let promise = new Promise<GoogleLocation>(() => {
        let location = new GoogleLocation();
        navigator.geolocation.getCurrentPosition(position => {
            location.latitude = position.coords.latitude;
            location.longitude = position.coords.longitude;
        });
        return location;
    });

    return promise;
    }
}

所以我的问题是我在等待时如何设置它。所以当我试图访问它时它就在那里？

Answer 1

你永远不会在getLocation中解决你的承诺，所以await自然会永远等待。从承诺执行者（您传递给new Promise）的函数中返回一个值并不能解决这个承诺，并注意您尝试返回的内容，您和＆＃t> ＃39;在填写坐标之前重新返回too early。

相反，接受promise执行函数中的resolve和reject参数并使用它们：

private getLocation(): Promise<GoogleLocation> {
    return new Promise<GoogleLocation>((resolve, reject) => {
        navigator.geolocation.getCurrentPosition(position => {
            if (/*...it didn't work...*/) {
                reject(new Error(/*...*/));
            } else {
                // It worked
                const location = new GoogleLocation();
                location.latitude = position.coords.latitude;
                location.longitude = position.coords.longitude;
                resolve(location);
                // Maybe you could just `resolve(position.coords)`?
            }
        });
    });
}

附注：如果您宣传地理定位服务，那么您根本不需要new Promise。

打字稿承诺并等待

1 个答案: