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angular - 打字稿函数中的错误-函数缺少结束返回语句并且返回类型不包括“未定义”

问题描述

我在 createBreadcrumbs 函数中遇到错误（'函数缺少结束返回语句并且返回类型不包括 'undefined'.ts(2366)'）。请解释为什么我收到错误以及如何解决？

export class BreadcrumbComponent implements OnInit {

  static readonly ROUTE_DATA_BREADCRUMB = 'breadcrumb';
  readonly home = {icon: 'pi pi-home', url: 'home'};
  menuItems!: MenuItem[];

  constructor(private router: Router, private activatedRoute: ActivatedRoute) {}

  ngOnInit(): void {
    this.router.events
      .pipe(filter(event => event instanceof NavigationEnd))
      .subscribe(() => this.menuItems = this.createBreadcrumbs(this.activatedRoute.root));
  }

  private createBreadcrumbs(route: ActivatedRoute, url: string = '#', breadcrumbs: MenuItem[] = []): MenuItem[] {
    const children: ActivatedRoute[] = route.children;

    if (children.length === 0) {
      return breadcrumbs
    } 

    for (const child of children) {
      const routeURL: string = child.snapshot.url.map(segment => segment.path).join('/');
      if (routeURL !== '') {
        url += `/${routeURL}`;
      }

      const label = child.snapshot.data[BreadcrumbComponent.ROUTE_DATA_BREADCRUMB];
      if (label !== null || label !== undefined) {
        breadcrumbs.push({label, url});
      }

      return this.createBreadcrumbs(child, url, breadcrumbs);
    }
  
    
  }

}

标签： angulartypescript

解决方案

看来Typescript的编译器不明白，如果数组的长度不为零的话，肯定会入贷并返回一个值。

所以，简单的灵魂是这样的：

  private createBreadcrumbs(route: ActivatedRoute, url: string = '#', breadcrumbs: MenuItem[] = []): MenuItem[] {
    const children: ActivatedRoute[] = route.children;

    for (const child of children) {
      const routeURL: string = child.snapshot.url.map(segment => segment.path).join('/');
      if (routeURL !== '') {
        url += `/${routeURL}`;
      }

      const label = child.snapshot.data[BreadcrumbComponent.ROUTE_DATA_BREADCRUMB];
      if (label !== null || label !== undefined) {
        breadcrumbs.push({label, url});
      }

      return this.createBreadcrumbs(child, url, breadcrumbs);
    }

    // if (children.length === 0)
    return breadcrumbs;
  }

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