Angular2 CanActivate state.url infinite loop

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**Redirection to state.url within subscription to observable in CanActivate causes infinite loop**   

    canActivate(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): boolean{

/* to store and redirect after login if user not logged in */

let target_url: string = state.url;

let adminSubj = new Subject<boolean>();

return this.verifyLoginForAdmin( target_url );

}

verifyLoginForAdmin( target_url: string ){

if( this.authService.isLoggedin() ){

let token_email = 

this.authService

.jwt_helper

.decodeToken( localStorage.getItem(this.authService.jwt_name ) ).email;

this.authService.isAdmin( token_email )

.subscribe({ 

next:  data => {

if( data ){

                        this.router.navigate( [ target_url ]);

return true;

}

else{

this.router.navigate( [ '/coding-blog' ]);

return false;

}

},

error: error => console.log("CanActivate Error-->", error),

complete: () => console.log("done");

})

}

this.authService.targetUrl = target_url;

this.router.navigate( [ '/coding-blog' ] );

return false;

}

} 

**authService#isAdmin() is:**  

    isAdmin( email: string ): Observable<boolean>{

return this.getDbInfo

.getOneUserByEmail( email )

.map( res => res.json().data.admin );

    }

In another route protected by a different CanActivate implementation  

I have the same set up with the `target_url`  

and it never goes into a perpetual loop.  

 

    canActivate(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): boolean {

let targetUrl: string = state.url;

return this.verifyLogin( targetUrl, route.params['name'] );

}

verifyLogin(target_url: string, target_user: string): boolean{

if( this.authService.isLoggedin() ){

let token_name = 

this.authService

.jwt_helper

.decodeToken( localStorage.getItem( this.authService.jwt_name ) )

.name;

if( token_name === target_user){

this.router.navigate([ target_url ]);

return true;

}

else{

this.router.navigate([ '/projects' ]);

return false;

}

}

this.authService.targetUrl = target_url;

this.router.navigate([ '/projects' ]);

return false;

}

    }

**It seems to be the subscription that is doing the  

black magic in this sense.**  

Obviously I am not understanding this part of this  

technology very well.  

I think I am lost within Rxjs and Angular2 .. somehow ...somewhere ....  

Help please.