Angular 订阅服务中的变量时出现问题

我正在学习Angular并尝试侦听一个包含http请求值的变量。这是服务

export class UsersService {
 message = new Subject<string>();
 constructor(private http: HttpClient) { }
 addUser(userData: {username, email, password, school}) {
   this.http.post<any>('http://127.0.0.1/apiapp/insert.php', userData).subscribe( (r) => {
     this.message = r.message;
   });
}

我得到一个空白的数据，没有任何记录，只是控制台中的一个空白行。这是为什么？如何解决？

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提前感谢

您这里有3个问题

您没有通过主题正确发送值 您的console.logthis.result的位置存在一些异步问题 您需要调用.asObservable对您的主题进行观察，以使主题成为可观察的

export class UsersService {
    message = new Subject<string>();
    constructor(private http: HttpClient) { }

    addUser(userData: {username, email, password, school}) {
        this.http.post<any>('http://127.0.0.1/apiapp/insert.php', userData).subscribe( (r) => {
        // .next is how you send data via a subject
        this.message.next(r.message);
    });
}




result = '';
private resultSubscription: Subscription;

ngOnInit() {
    // Get subject as observable
    this.resultSubscription = this.userS.message.asObservable().subscribe( (r) => {
        this.result = r;
        // by logging here we can ensure that the result will be populated
        console.log(this.result);  
    });
}

addPost(userData: {username: string, email: string, password: string, school: string}) {
    this.userS.addUser(userData);
}

// It is important to unsubscribe for your observable when the component is destroyed
ngOnDestroy(): void { this.resultSubscription.unsubscribe(); }

---

Ngondestory:void{this.resultSubscription.unsubscribe；}在这种情况下，这对于防止内存泄漏很重要，对吗？@PHPUser你是对的，完全忘记了这一点。我的道歉

export class UsersService {
    message = new Subject<string>();
    constructor(private http: HttpClient) { }

    addUser(userData: {username, email, password, school}) {
        this.http.post<any>('http://127.0.0.1/apiapp/insert.php', userData).subscribe( (r) => {
        // .next is how you send data via a subject
        this.message.next(r.message);
    });
}




result = '';
private resultSubscription: Subscription;

ngOnInit() {
    // Get subject as observable
    this.resultSubscription = this.userS.message.asObservable().subscribe( (r) => {
        this.result = r;
        // by logging here we can ensure that the result will be populated
        console.log(this.result);  
    });
}

addPost(userData: {username: string, email: string, password: string, school: string}) {
    this.userS.addUser(userData);
}

// It is important to unsubscribe for your observable when the component is destroyed
ngOnDestroy(): void { this.resultSubscription.unsubscribe(); }