Error ExpressionChangedAfterItHasBeenCheckedError is a common error that occurs in Angular applications when there are changes to a bound property or expression after Angular has finished its change detection cycle. This error typically occurs when there is a change that happens inside a lifecycle hook or an asynchronous operation triggers a change.
When using router.events and navigate in Angular, it is possible to encounter the ExpressionChangedAfterItHasBeenCheckedError because the change detection mechanism in Angular may not have had a chance to complete its cycle before the navigation operation is triggered.
To fix this error, there are a few steps you can follow:
- Use the ngAfterViewInit lifecycle hook:
- Make sure you have imported the AfterViewInit interface from @angular/core.
- Implement the ngAfterViewInit method in your component.
- Move your code that triggers the navigation inside the ngAfterViewInit method.
import { Component, AfterViewInit } from '@angular/core';
@Component({
selector: 'app-my-component',
template: '...'
})
export class MyComponent implements AfterViewInit {
ngAfterViewInit() {
// Code that triggers navigation goes here
}
}
By using ngAfterViewInit, you ensure that the navigation code is run after the component's view has been initialized, allowing Angular to complete its change detection cycle before the navigation happens.
- Use a setTimeout:
- Wrap the code that triggers navigation inside a setTimeout function.
- Set the timeout duration to 0 or a small value.
setTimeout(() => {
// Code that triggers navigation goes here
}, 0);
Using setTimeout allows the change detection to complete its cycle before the navigation operation is triggered. By setting the timeout duration to 0 or a small value, the code inside the setTimeout function will be executed as soon as possible.
It's important to note that using setTimeout should be considered as a workaround and should be used sparingly. It may have a negative impact on performance, especially if used in a large-scale application.
In conclusion, to fix the ExpressionChangedAfterItHasBeenCheckedError when using router.events and navigate in Angular, you can either use the ngAfterViewInit lifecycle hook or wrap the navigation code inside a setTimeout function. Both approaches ensure that the change detection cycle is completed before the navigation operation happens, preventing the error from occurring.