0

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承诺运行良好。

问题是在解决承诺之前加载了 html 页面，因此显示的值是未定义的。

承诺解决后，我可以使用什么来加载页面以及如何加载？

文件共享.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() {

  }


}

文件共享.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>

共享模型.model.ts

export class ShareModel {
    Id:number;
    Name: string;
    Description: string;
    Syntax: string;
    IdentityString:string;
    LastModified: string;
    Content: string;
    FileId: number;
}
4

2 回答 2

0

或者更简单地说，您可以?.在 html 模板中使用 elvis 运算符。

文件共享.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>
于 2020-01-05T13:05:07.727 回答
0

由于FileShareComponent是触发服务调用的那个，除非您创建更复杂的嵌套组件体系结构，否则在该调用完成之前，您将无法阻止组件初始化。

在 Observable 解决之前，我会隐藏这些值。而且我认为没有紧迫的理由将 Observable 转换为 Promise。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一个隐藏的 div 中，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>

我认为这是根据您当前的结构让您前进的最简单方法。如果我从头开始构建它，我会考虑使用路由器解析器。

于 2020-01-05T12:58:39.880 回答