What could be causing the ngOnInit() method to execute before canActivate() in this scenario

Question

What could be causing the ngOnInit() method to execute before canActivate() in this scenario

When working with route guards, I am using the canActivate() method. However, I have noticed that Angular is triggering the ngOnInit() of my root AppComponent before calling canActivate.

In my scenario, I need to ensure that certain data is fetched in the canActivate function before rendering it in the template of the AppComponent.

Is there a way to handle this situation effectively?

javascript angular typescript view canactivate

Answer 1

Answer №1

When faced with such cases, this is my usual approach:

1. I start by creating a Resolver service that implements the Resolve interface. This service ensures that all necessary data is retrieved before activating the route:

import { Injectable } from '@angular/core';
import { ActivatedRouteSnapshot, Resolve, RouterStateSnapshot } from '@angular/router';
import { DataService } from 'path/to/data.service';

@Injectable()
export class ExampleResolverService implements Resolve<any> {
  constructor(private _dataService: DataService) { }

  resolve(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): Promise<any> {
    return this._dataService.anyAsyncCall()
      .then(response => {
        /* Assume the method returns a response with a field "result" that can be either "true" or "false" */
        /* "setResult" simply stores the passed argument in the "DataService" class property */
        this._dataService.setResult(response.result);
      })
      .catch(err => this._dataService.setResult(false););
  }
}

2. Next, let's consider how to handle the AuthGuard, which implements the CanActivate interface:

import { Injectable } from '@angular/core';
import { ActivatedRouteSnapshot, CanActivate, Router, RouterStateSnapshot } from '@angular/router';
import { DataService } from 'path/to/data.service';

@Injectable()
export class AuthGuard implements CanActivate {
  constructor(private _dataService: DataService) { }

  canActivate(route: ActivatedRouteSnapshot, state: RouterStateSnapshot) {
    /* The "getResult" method works with the same class property as setResult, but it only returns its value */
    return this._dataService.getResult(); // will return either "true" or "false"
  }
}

3. Finally, incorporate the Resolver and AuthGuard into your routes configuration. Here is an example structure (the actual route setup may vary, but this provides a basis for including the parent component activation):

const routes: Routes = [
  {
    path: 'app',
    component: AppComponent,
    resolve: {
      result: ExampleResolverService // your resolver
    },
    canActivate: [AuthGuard], // your AuthGuard with "canActivate" method
    children: [...] // child routes are defined within this array
  }
];

Functionality Overview

Upon navigating to /app, the ExampleResolverService initiates, executes the API call, and saves the required part of the response in a class property within DataService using the setResult method (a standard setter operation). Subsequently, the AuthGuard comes into play after the completion of the resolver task. It retrieves the stored result from DataService through the getResult method (a traditional getter), and subsequently returns this boolean result (since the AuthGuard expects a boolean outcome for activation – returning true activates the route while false prevents activation).

This example offers a basic framework without extra data manipulations. Typically, the logic is more intricate, but this foundation should suffice for fundamental comprehension.

Answer 2

When faced with such cases, this is my usual approach:

1. I start by creating a Resolver service that implements the Resolve interface. This service ensures that all necessary data is retrieved before activating the route:

import { Injectable } from '@angular/core';
import { ActivatedRouteSnapshot, Resolve, RouterStateSnapshot } from '@angular/router';
import { DataService } from 'path/to/data.service';

@Injectable()
export class ExampleResolverService implements Resolve<any> {
  constructor(private _dataService: DataService) { }

  resolve(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): Promise<any> {
    return this._dataService.anyAsyncCall()
      .then(response => {
        /* Assume the method returns a response with a field "result" that can be either "true" or "false" */
        /* "setResult" simply stores the passed argument in the "DataService" class property */
        this._dataService.setResult(response.result);
      })
      .catch(err => this._dataService.setResult(false););
  }
}

2. Next, let's consider how to handle the AuthGuard, which implements the CanActivate interface:

import { Injectable } from '@angular/core';
import { ActivatedRouteSnapshot, CanActivate, Router, RouterStateSnapshot } from '@angular/router';
import { DataService } from 'path/to/data.service';

@Injectable()
export class AuthGuard implements CanActivate {
  constructor(private _dataService: DataService) { }

  canActivate(route: ActivatedRouteSnapshot, state: RouterStateSnapshot) {
    /* The "getResult" method works with the same class property as setResult, but it only returns its value */
    return this._dataService.getResult(); // will return either "true" or "false"
  }
}

3. Finally, incorporate the Resolver and AuthGuard into your routes configuration. Here is an example structure (the actual route setup may vary, but this provides a basis for including the parent component activation):

const routes: Routes = [
  {
    path: 'app',
    component: AppComponent,
    resolve: {
      result: ExampleResolverService // your resolver
    },
    canActivate: [AuthGuard], // your AuthGuard with "canActivate" method
    children: [...] // child routes are defined within this array
  }
];

Functionality Overview

Upon navigating to /app, the ExampleResolverService initiates, executes the API call, and saves the required part of the response in a class property within DataService using the setResult method (a standard setter operation). Subsequently, the AuthGuard comes into play after the completion of the resolver task. It retrieves the stored result from DataService through the getResult method (a traditional getter), and subsequently returns this boolean result (since the AuthGuard expects a boolean outcome for activation – returning true activates the route while false prevents activation).

This example offers a basic framework without extra data manipulations. Typically, the logic is more intricate, but this foundation should suffice for fundamental comprehension.

Answer 3

Answer №2

My approach involved listening for ROUTE_NAVIGATED events within the app component as demonstrated below:

To achieve this functionality, I opted to utilize ngrx/router-store in order to monitor these router actions.

// app.component.ts
public ngOnInit(): void {
  // Obtain the action stream
  this.actions$.pipe(
    // Focus only on completed router actions 
    ofType(ROUTER_NAVIGATED),
    // Now that the resolve has finished (since the router is done), switch to further processing
    switchMap(() => {
      // Proceed to retrieve the desired data
      return this.someService.getStuff();
    })
  // Subscription to actions is necessary since we are in the component, not an effect
  // Although unsubscription may be ideal, the app component will likely persist throughout, continuously listening
  ).subscribe();

Answer 4

My approach involved listening for ROUTE_NAVIGATED events within the app component as demonstrated below:

To achieve this functionality, I opted to utilize ngrx/router-store in order to monitor these router actions.

// app.component.ts
public ngOnInit(): void {
  // Obtain the action stream
  this.actions$.pipe(
    // Focus only on completed router actions 
    ofType(ROUTER_NAVIGATED),
    // Now that the resolve has finished (since the router is done), switch to further processing
    switchMap(() => {
      // Proceed to retrieve the desired data
      return this.someService.getStuff();
    })
  // Subscription to actions is necessary since we are in the component, not an effect
  // Although unsubscription may be ideal, the app component will likely persist throughout, continuously listening
  ).subscribe();

What could be causing the ngOnInit() method to execute before canActivate() in this scenario

Answer №1

Functionality Overview

Answer №2

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