输入“布尔值 | undefined' 不可分配给类型 'boolean'。 类型“undefined”不可分配给类型“boolean”

Question

Hello I'm workig in an angular project with php. But I have this error "Type 'boolean | undefined' is not assignable to type 'boolean'. Type 'undefined' is not assignable to type 'boolean'" in this line "return this.isLogin(routeurl);". How can I solve it please?

import { Injectable } from '@angular/core';
import { ActivatedRouteSnapshot, RouterStateSnapshot, UrlTree, CanActivate, Router } from 
'@angular/router';
import { ApiService } from './api.service';

@Injectable({
providedIn: 'root'
})

export class AuthguardGuard implements CanActivate {
constructor(private dataService: ApiService,private router: Router ) {}
canActivate(
route: ActivatedRouteSnapshot,
state: RouterStateSnapshot): boolean {
const routeurl: string = state.url;
return this.isLogin(routeurl);
}

isLogin(routeurl: string) {
if (this.dataService.isLoggedIn()) {
return true;
}

this.dataService.redirectUrl = routeurl;
this.router.navigate(['/login'], {queryParams: { returnUrl: routeurl }} );
}
}

I have also this error "(method) AuthguardGuard.isLogin(routeurl: string): true | undefined Not all code paths return a value." in this line "isLogin(routeurl: string) " thanks in advance

Answer 1

Typescript complains that you return a value of type boolean | undefined boolean | undefined when it expects it to be just boolean .

Assuming the return type of this.isLogin(routeurl) is boolean | undefined boolean | undefined you could simply return a default value when it actually is ùndefined .

return this.isLogin(routeurl) ?? false;

For your second problem you simply have to return something at the end of the method:

isLogin(routeurl: string) {
if (this.dataService.isLoggedIn()) {
return true;
}

this.dataService.redirectUrl = routeurl;
this.router.navigate(['/login'], {queryParams: { returnUrl: routeurl }} );
return;
}

Answer 2

The undefined is diff from the boolean. If your function can return undefined you need to explicit this like:

canActivate(
  route: ActivatedRouteSnapshot,
  state: RouterStateSnapshot): boolean | undefined {
  const routeurl: string = state.url;
  return this.isLogin(routeurl);
}