角度4:如何将应用程序级http错误作为可观察错误正确处理?

    return this.userService
        .create(user)
        .map(
            json => { 
                console.log(json);
                if (json.status=='error') {
                    console.log('error return throw');
                    return Observable.throw('Credentials mismatch or not existing');
                }

                const user = json.data as User;    
                return user;
            },
            err => { 
                console.log(err);
            }
        );

在我的歌唱中。组件,我这样做:

    onSubmit() {
        // blahblah

        this.si
        .signUp(this.credentials.emailAddress, this.credentials.password, this.credentials.zipCode)
        .subscribe(
        user => {
            console.log(user);
            console.log(`SignUpComponent.onSubmit() found user.userId ${user.userId}`);
            this.router.navigate(['signin']);
        },
        err => {
            this.errorMessage = `*** SignUpComponent: Error while signing up {err}`;
            console.error('*** SignUpComponent: Error while signing up', err);
            this.resume();
            //this.router.navigate(['signup']);
        });

        this.ngOnChanges();
    }

我希望能触发err关闭。

我错过了什么?

[Log] SigninService.signUp, zipCode=
[Log] {data: null, status: "error", message: "Error user create: - missing id   API usage v1b3: Tu…ate\"}↵post: []↵.↵", ws: "v1b3: Tuesday, August 25th 2017 20h20 @ Tanger"}
[Log] error return throw
[Log] ErrorObservable {_isScalar: false, error: "Credentials mismatch or not existing", scheduler: undefined, _subscribe: function, …}
[Log] SignUpComponent.onSubmit() found user.userId undefined