我需要你的帮助,我正在尝试显示来自我的 firebase 的一些数据,但它给我带来了类似
InvalidPipeArgument: '[object Object]' for pipe 'AsyncPipe'
的错误。
我的服务是:
import { Injectable } from '@angular/core';
import { AngularFireDatabase } from 'angularfire2/database';
@Injectable()
export class MoviesService {
constructor(private db: AngularFireDatabase) {}
get = () => this.db.list('/movies');
}
这是我的组件:
import { Component, OnInit } from '@angular/core';
import { MoviesService } from './movies.service';
@Component({
selector: 'app-movies',
templateUrl: './movies.component.html',
styleUrls: ['./movies.component.css']
})
export class MoviesComponent implements OnInit {
movies: any[];
constructor(private moviesDb: MoviesService) { }
ngOnInit() {
this.moviesDb.get().subscribe((snaps) => {
snaps.forEach((snap) => {
this.movies = snap;
console.log(this.movies);
});
});
}
}
还有哈巴狗妈妈:
ul
li(*ngFor='let movie of (movies | async)')
| {{ movie.title | async }}
async
用于绑定到 Observables 和 Promises,但看起来你正在绑定到一个常规对象。您只需删除两个 async
关键字就可以了。
当您在模板中使用异步,但引用的对象不是 Observable 时,您会收到此消息。
为了举例,假设我的类中有这些属性:
job:Job
job$:Observable<Job>
然后在我的模板中,我这样引用它:
{{job | async }}
而不是:
{{job$ | async }}
如果使用异步管道,则不需要 job:Job 属性,但它可以说明错误的原因。
在您的 MoviesService 中,您应该导入 FirebaseListObservable 以便定义返回类型
FirebaseListObservable<any[]>
import { AngularFireDatabase, FirebaseListObservable } from 'angularfire2/database';
那么 get() 方法应该是这样的-
get (): FirebaseListObservable<any[]>{
return this.db.list('/movies');
}
此 get() 方法将返回电影列表的 FirebaseListObervable
在你的 MoviesComponent 中应该看起来像这样
export class MoviesComponent implements OnInit {
movies: any[];
constructor(private moviesDb: MoviesService) { }
ngOnInit() {
this.moviesDb.get().subscribe((snaps) => {
this.movies = snaps;
});
}
}
然后你可以轻松地迭代电影而无需异步管道,因为电影[]数据不是可观察类型,你的html应该是这样的
ul
li(*ngFor='let movie of movies')
{{ movie.title }}
如果您将电影声明为
movies: FirebaseListObservable<any[]>;
那么您只需致电
movies: FirebaseListObservable<any[]>;
ngOnInit() {
this.movies = this.moviesDb.get();
}
你的html应该是这样的
ul
li(*ngFor='let movie of movies | async')
{{ movie.title }}
我找到了另一种获取数据的解决方案。根据文档请检查文档链接
在服务文件中添加以下内容。
import { Injectable } from '@angular/core';
import { AngularFireDatabase } from 'angularfire2/database';
@Injectable()
export class MoviesService {
constructor(private db: AngularFireDatabase) {}
getMovies() {
this.db.list('/movies').valueChanges();
}
}
在组件中添加以下内容。
import { Component, OnInit } from '@angular/core';
import { MoviesService } from './movies.service';
@Component({
selector: 'app-movies',
templateUrl: './movies.component.html',
styleUrls: ['./movies.component.css']
})
export class MoviesComponent implements OnInit {
movies$;
constructor(private moviesDb: MoviesService) {
this.movies$ = moviesDb.getMovies();
}
在您的 html 文件中添加以下内容。
<li *ngFor="let m of movies$ | async">{{ m.name }} </li>
您应该将管道添加到
interpolation
而不是 ngFor
ul
li(*ngFor='let movie of (movies)') ///////////removed here///////////////////
| {{ movie.title | async }}
好吧,我现在遇到了类似的问题,我解决了,所以让我解释一下你可以做什么,但首先我不知道你使用的是哪个版本的 Angular,所以方法可能不同,我在下面添加我的设置版本
Angular CLI: 13.3.1
Node: 16.14.2
Package Manager: npm 8.5.0
OS: win32 x64
Angular: 13.3.1
... animations, cli, common, compiler, compiler-cli, core, forms
... platform-browser, platform-browser-dynamic, router
Package Version
@angular-devkit/architect 0.1303.1
@angular-devkit/build-angular 13.3.1
@angular-devkit/core 13.3.1
@angular-devkit/schematics 13.3.1
@angular/fire 7.3.0
@schematics/angular 13.3.1
rxjs 7.5.5
typescript 4.6.3
1 第一个更改是您的服务文件,将其更改为
import { Injectable } from '@angular/core';
import { AngularFireDatabase } from 'angularfire2/database';
@Injectable()
export class MoviesService {
constructor(private db: AngularFireDatabase) {}
get = () => this.db.list('/movies');
}
对此,
import { Injectable } from '@angular/core';
import { AngularFireDatabase } from 'angularfire2/database';
@Injectable()
export class MoviesService {
constructor(private db: AngularFireDatabase) {}
get = () => this.db.list('/movies');
}
注意:- 不要忘记从正确的模块导入 Observable
然后从此更改您的组件
import { Injectable } from '@angular/core';
import { AngularFireDatabase } from 'angularfire2/database';
@Injectable()
export class MoviesService {
constructor(private db: AngularFireDatabase) {}
get(): Observable<any[]>{
return this.db.list('/movies')
}
}
对于这样的事情
import { Injectable } from '@angular/core';
import { AngularFireDatabase } from 'angularfire2/database';
@Injectable()
export class MoviesService {
constructor(private db: AngularFireDatabase) {}
get(): Observable<any[]>{
return this.db.list('/movies')
}
}
还有你的最后一个文件
import { Component, OnInit } from '@angular/core';
import { MoviesService } from './movies.service';
@Component({
selector: 'app-movies',
templateUrl: './movies.component.html',
styleUrls: ['./movies.component.css']
})
export class MoviesComponent implements OnInit {
movies: any[];
constructor(private moviesDb: MoviesService) { }
ngOnInit() {
this.moviesDb.get().subscribe((snaps) => {
snaps.forEach((snap) => {
this.movies = snap;
console.log(this.movies);
});
});
}
}
对此
import { Component, OnInit } from '@angular/core';
import { MoviesService } from './movies.service';
@Component({
selector: 'app-movies',
templateUrl: './movies.component.html',
styleUrls: ['./movies.component.css']
})
export class MoviesComponent implements OnInit {
movies: any[];
constructor(private moviesDb: MoviesService) { }
ngOnInit() {
this.moviesDb.get().subscribe((snaps) => {
snaps.forEach((snap) => {
this.movies = snap;
console.log(this.movies);
});
});
}
}
我不是专业人士,但我用这种方式解决了它,希望它也适合你
如果您已将代码从使用
import { Component, OnInit } from '@angular/core';
import { MoviesService } from './movies.service';
@Component({
selector: 'app-movies',
templateUrl: './movies.component.html',
styleUrls: ['./movies.component.css']
})
export class MoviesComponent implements OnInit {
movies$: any;
constructor(private moviesDb: MoviesService) { }
ngOnInit() {
this.movies$ = this.moviesDb.get()
.subscribe((snaps) => {
snaps.forEach((snap) => {
this.movies$ = snap;
console.log(this.movies$);
});
});
}
}
转换为 import { Component, OnInit } from '@angular/core';
import { MoviesService } from './movies.service';
@Component({
selector: 'app-movies',
templateUrl: './movies.component.html',
styleUrls: ['./movies.component.css']
})
export class MoviesComponent implements OnInit {
movies$: any;
constructor(private moviesDb: MoviesService) { }
ngOnInit() {
this.movies$ = this.moviesDb.get()
.subscribe((snaps) => {
snaps.forEach((snap) => {
this.movies$ = snap;
console.log(this.movies$);
});
});
}
}
,您可能会遇到以下错误变体:
ul
li(*ngFor='let movie of (movies | async)')
| {{ movie.title | async }}
“本机代码”部分乍一看有点吓人,但它只是带有唯一符号的信号的字符串表示形式。
只需单击错误消息中与您的代码类似的第一行代码,即可找到模板中您切换到使用信号但未更新
ul
li(*ngFor='let movie of (movies | async)')
| {{ movie.title | async }}
管道的位置。
所以之前您可能已经:
ul
li(*ngFor='let movie of (movies | async)')
| {{ movie.title }}
现在作为一个信号应该是:
Observable