Router Preventing Transitions Via willTransition

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It fires the willTransition action on currently active routes when you re-attempt the transition by using the {{link-to}} helper or the transitionTo method.

Syntax

Ember.Route.extend ({
   actions: {
      willTransition(transition) {
         //handle the transition
      }
   }
});

Example

The example given below depicts preventing transitions via the willTransition action on active route. Create a route called willtransition and open the router.js file with the following code to define URL mappings −

import Ember from 'ember';                   
//Access to Ember.js library as variable Ember
import config from './config/environment';
//It provides access to app's configuration data as variable config 

//The const declares read only variable
const Router = Ember.Router.extend ({
   location: config.locationType,
   rootURL: config.rootURL
});

Router.map(function() {
   this.route('willtransition');
});

//It specifies Router variable available to other parts of the app
export default Router;

Create the application.hbs file and add the following code −

//link-to is a handlebar helper used for creating links
{{link-to 'Click For Transition' 'willtransition'}}
{{outlet}} //It is a general helper, where content from other pages 
   will appear inside this section

Open the file willtransition.js file created under app/routes/ with the following code −

import Ember from 'ember';

export default Ember.Route.extend ({
   actions: {
      willTransition(transition) {
         
         //decalring the self variable
         var self = this;
         
         //checking whether self variable is false or not
         if (!this.get('allowTransition')) {
            document.write('<b><font color = "red">');
            
            //display the message
            document.write("transition abort");
            document.write('</font><br>');
            transition.abort();  //calling abort function

            Ember.run.later(function () {
               //setting the self variable to true
               self.set('allowTransition', true);
               document.write('<b><font color = "blue">');
               
               //display the message
               document.write("transition retry");
               document.write('</font>');
               transition.retry();  //calling retry function
            }, 500);
         }
      }
   }
});

Open the willtransition.hbs file created under app/templates/ with the following code −

<h2>Hello...Welcome to Tutorialspoint!!!</h2>
{{outlet}}

Output

Run the ember server and you will receive the following output −

When you click on the link, it will display the data. But if you click on the back link, the willTransition action calls the transition.abort() and then transition.retry() method.