Angular 发布到Firebase数据库参考之前的Firebase存储下载URL

与firebase合作完成angular 4项目

我正在努力解决如何确保在运行下一步之前，已从可观察对象返回结果的问题

我知道你不能保证有一个可观测的，因为整个问题是它是一个数据流，因此我的困境

我正在尝试将图像上载到firebase存储，在运行firebase数据库更新之前检索其下载URL

如有任何建议，将不胜感激

注册用户服务

$key: string;
    downloadUrl: string;
    currentUser: any;
    loginId: string;

    constructor(
        private db: AngularFireDatabase,
        private firebaseUploadService: FirebaseUploadService,
        private authService: AuthService) {
        this.firebaseUploadService.currentUrl.subscribe(url => this.downloadUrl = url);
    }

registerUser(firebaseRef: string, user: UserModel): Observable<any> {

        // Create a separate object for file upload with the file passed via the entity
        const file = Object.assign(<UploadModel>{}, user.imagePath);
        user.$key = this.authService.currentUserId;

        return this.firebaseUploadService.pushUpload(user.$key, file).switchMap(upload => {
            console.log('upload returned from service: ', upload)
            user.imagePath = this.downloadUrl;
            return Observable.fromPromise(this.db.object(firebaseRef + '/' + user.$key).update(user));
        });
    }

    currentUser: any;
    uploads: FirebaseListObservable<UploadModel[]>;

    private urlSource = new BehaviorSubject('http://saveabandonedbabies.org/wp-content/uploads/2015/08/default.png');
    currentUrl = this.urlSource.asObservable();

    constructor() {
    }

pushUpload(firebaseRef: string, upload: UploadModel): any {

        const storageRef = firebase.storage().ref();
        const uploadTask = storageRef.child(`${firebaseRef}/${upload.file.name}`).put(upload.file);

        uploadTask.on(firebase.storage.TaskEvent.STATE_CHANGED,
            (snapshot) => {
                // upload in progress
                upload.progress = (snapshot.bytesTransferred / snapshot.totalBytes) * 100
            },
            (error) => {
                // upload failed
                console.log(error)
            },
            () => {
                // upload success
                upload.url = uploadTask.snapshot.downloadURL
                this.urlSource.next(upload.url)
                upload.name = upload.file.name
            }
        );
        return this.urlSource;
    }

$key:string；
下载URL:string；
当前用户：任何；
loginId:string；
建造师(
私有数据库：AngularFireDatabase，
私有firebaseUploadService:firebaseUploadService，
专用身份验证服务：身份验证服务）{
this.firebaseuloadservice.currentUrl.subscribe（url=>this.downloadUrl=url）；
}
registerUser（firebaseRef:string，user:UserModel）：可观察{
//使用通过实体传递的文件为文件上载创建单独的对象
const file=Object.assign（{}，user.imagePath）；
user.$key=this.authService.currentUserId；
返回此.firebaseUploadService.pushUpload（用户.$key，文件）.switchMap（上载=>{
log（'从服务返回的上载：'，上载）
user.imagePath=this.downloadUrl；
返回Observable.fromPromise（这个.db.object（firebaseRef+'/'+user.$key）.update（user））；
});
}

Firebase上传服务

$key: string;
    downloadUrl: string;
    currentUser: any;
    loginId: string;

    constructor(
        private db: AngularFireDatabase,
        private firebaseUploadService: FirebaseUploadService,
        private authService: AuthService) {
        this.firebaseUploadService.currentUrl.subscribe(url => this.downloadUrl = url);
    }

registerUser(firebaseRef: string, user: UserModel): Observable<any> {

        // Create a separate object for file upload with the file passed via the entity
        const file = Object.assign(<UploadModel>{}, user.imagePath);
        user.$key = this.authService.currentUserId;

        return this.firebaseUploadService.pushUpload(user.$key, file).switchMap(upload => {
            console.log('upload returned from service: ', upload)
            user.imagePath = this.downloadUrl;
            return Observable.fromPromise(this.db.object(firebaseRef + '/' + user.$key).update(user));
        });
    }

    currentUser: any;
    uploads: FirebaseListObservable<UploadModel[]>;

    private urlSource = new BehaviorSubject('http://saveabandonedbabies.org/wp-content/uploads/2015/08/default.png');
    currentUrl = this.urlSource.asObservable();

    constructor() {
    }

pushUpload(firebaseRef: string, upload: UploadModel): any {

        const storageRef = firebase.storage().ref();
        const uploadTask = storageRef.child(`${firebaseRef}/${upload.file.name}`).put(upload.file);

        uploadTask.on(firebase.storage.TaskEvent.STATE_CHANGED,
            (snapshot) => {
                // upload in progress
                upload.progress = (snapshot.bytesTransferred / snapshot.totalBytes) * 100
            },
            (error) => {
                // upload failed
                console.log(error)
            },
            () => {
                // upload success
                upload.url = uploadTask.snapshot.downloadURL
                this.urlSource.next(upload.url)
                upload.name = upload.file.name
            }
        );
        return this.urlSource;
    }

currentUser:any；
上传：FirebaseListObservable；
私有urlSource=新行为主体（'http://saveabandonedbabies.org/wp-content/uploads/2015/08/default.png');
currentUrl=this.urlSource.asObservable（）；
构造函数（）{
}
pushUpload（firebaseRef:string，upload:UploadModel）：任意{
const storageRef=firebase.storage（）.ref（）；
const uploadTask=storageRef.child（`${firebaseRef}/${upload.file.name}'）.put（upload.file）；
uploadTask.on（firebase.storage.TaskEvent.STATE_已更改，
（快照）=>{
//正在上载
upload.progress=（snapshot.bytesttransfered/snapshot.totalBytes）*100
},
（错误）=>{
//上载失败
console.log（错误）
},
() => {
//上传成功
upload.url=uploadTask.snapshot.downloadURL
this.urlSource.next（upload.url）
upload.name=upload.file.name
}
);
返回此.urlSource；
}

由于所有Firebase调用都是异步的，因此无法同步获取下载url。但是有一个骗局，你可以通过承诺来做到

尝试按如下方式重构代码：

pushUpload（firebaseRef:string，upload:UploadModel）：任意{

这可能有用