我正在尝试使用Angular和Typescript从ASP .NET Core API向html组件显示一些数据,响应返回正确的值,并且Promise正常工作。
问题是在解决诺言之前加载了html页面,因此显示的值是不确定的。
在解决诺言之后,我可以使用什么来使页面加载?
fileshare.component.ts
export class FileShareComponent implements OnInit {
constructor(
private route: ActivatedRoute,
private router: Router,
private service: UserService,
private http: HttpClient
) {
const file: string = this.route.snapshot.queryParamMap.get('file');
this.http.get(this.service.BaseURL + '/Share?IdentityString=' + file)
.toPromise()
.then(res => {
this.service.sharedFormData = res as ShareModel;
console.log(this.service.sharedFormData);
});
}
ngOnInit() {
}
}
fileshare.component.html
<pre><code class="hljs">Name:
{{service.sharedFormData.Name}}</code></pre>
<pre><code class="hljs">Description:
{{service.sharedFormData.Description}}</code></pre>
<pre><code class="hljs">Syntax:
{{service.sharedFormData.Syntax}}</code></pre>
<pre><code class="hljs">LastModified:
{{service.sharedFormData.LastModified | date: "HH:mm dd/MM/yyyy"}}</code></pre>
<pre><code class="hljs">Content:
{{service.sharedFormData.Content}}</code></pre>
<div class="form-group text-center mt-4">
<button class="btn btn-dark" (click)="this.service.raw()" type="submit"><i class="fas fa-database"></i>
Raw</button>
</div>
share-model.model.ts
export class ShareModel {
Id:number;
Name: string;
Description: string;
Syntax: string;
IdentityString:string;
LastModified: string;
Content: string;
FileId: number;
}
由于FileShareComponent
是触发服务调用的那个,除非创建了更为复杂的嵌套组件体系结构,否则您将无法阻止组件初始化,直到该调用完成为止。
我会隐藏这些值,直到Observable解析为止。而且,我认为没有紧迫的理由将可观察者转化为承诺。像这样的东西:
export class FileShareComponent implements OnInit {
// create a variable to determine whether screen is initialized
screenInitialized = false;
constructor(
private route: ActivatedRoute,
private router: Router,
private service: UserService,
private http: HttpClient
) {
const file: string = this.route.snapshot.queryParamMap.get('file');
this.http.get(this.service.BaseURL + '/Share?IdentityString=' + file)
// subscribe to Observable instead of converting it to a promise
.subscribe(res => {
this.service.sharedFormData = res as ShareModel;
// toggle initialized property
this.initialized = true;
console.log(this.service.sharedFormData);
});
}
ngOnInit() {
}
}
现在,只需将显示模板包装在div中,该div将一直隐藏直到加载数据:
<div *ngIf="initialized">
<pre><code class="hljs">Name:
{{service.sharedFormData.Name}}</code></pre>
<pre><code class="hljs">Description:
{{service.sharedFormData.Description}}</code></pre>
<pre><code class="hljs">Syntax:
{{service.sharedFormData.Syntax}}</code></pre>
<pre><code class="hljs">LastModified:
{{service.sharedFormData.LastModified | date: "HH:mm dd/MM/yyyy"}}</code></pre>
<pre><code class="hljs">Content:
{{service.sharedFormData.Content}}</code></pre>
<div class="form-group text-center mt-4">
<button class="btn btn-dark" (click)="this.service.raw()" type="submit"><i class="fas fa-database"></i>
Raw</button>
</div>
</div>
我认为这是根据当前结构开始工作的最简单方法。如果我是从头开始构建它,那么我会考虑使用router resolver。
或更简单地说,您可以在HTML模板中使用Elvis运算符?.
。
fileshare.component.html
<pre><code class="hljs">Name:
{{service?.sharedFormData?.Name}}</code></pre>
<pre><code class="hljs">Description:
{{service?.sharedFormData?.Description}}</code></pre>
<pre><code class="hljs">Syntax:
{{service?.sharedFormData?.Syntax}}</code></pre>
<pre><code class="hljs">LastModified:
{{service?.sharedFormData?.LastModified | date: "HH:mm dd/MM/yyyy"}}</code></pre>
<pre><code class="hljs">Content:
{{service?.sharedFormData?.Content}}</code></pre>
<div class="form-group text-center mt-4">
<button class="btn btn-dark" (click)="this.service.raw()" type="submit"><i class="fas fa-database"></i>
Raw</button>
</div>