Скачать или смотреть How to Pass a Component as a Parameter in Angular Click Events

Discover how to easily pass the clicked Angular component itself as a parameter in your event handlers. Learn step-by-step how to capture the right component within ngFor loops.
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This video is based on the question https://stackoverflow.com/q/67999037/ asked by the user 'Sadra M.' ( https://stackoverflow.com/u/8424269/ ) and on the answer https://stackoverflow.com/a/67999275/ provided by the user 'JackySky' ( https://stackoverflow.com/u/12449740/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the Problem: Capturing Component in Angular Click Events

When working with Angular's component-based architecture, you might find yourself in a situation where you want an event handler to know exactly which component triggered it, especially when you're dynamically generating components using *ngFor. This can be particularly challenging, as the typical click event binding doesn't directly give you access to the instance of the component that was clicked.

In this post, we'll explore a common scenario where you want to pass the clicked component as a parameter to an event handler and the steps to achieve this. Let’s break it down and see a simple solution to this problem.

The Scenario

In our situation, we have several instances of MyComponent being rendered through an ngFor loop, and we need to handle clicks in such a way that the clicked instance can be passed to the event handler. Here’s a snippet of what your original code might look like:

[[See Video to Reveal this Text or Code Snippet]]

The Challenge

You may have encountered issues with the following methods you’ve tried:

Template Variable: You attempted to create a template variable (like # comp), but it resulted in an empty object.

Using this: Relying on this gives you access to the parent component, not the current instance.

Sending $event: Passing the $event object only gets you the HTML element rather than the full component instance.

The goal is clear: we want to capture the whole instance of MyComponent in the click event handler so we can access its properties and methods directly.

Solution: Using Template Variables

The most straightforward way to pass the clicked component itself to an event handler is by using Angular template variables combined with ng-container. Here’s how you can revise your implementation:

Revised Template

Instead of calling your event handler with a generic variable, utilize a template variable to reference the component directly:

[[See Video to Reveal this Text or Code Snippet]]

Breakdown of the Code

Using ng-container: This acts as a structural directive that doesn't add extra elements to the DOM, allowing for cleaner implementation without unnecessary wrappers.

Defining a Template Variable: # component acts as a reference to the specific instance of MyComponent being created in the loop.

Click Event Binding: When the user clicks a component, pageClicked(component) directly sends the specific instance of MyComponent to the handler, allowing you to interact with its properties and methods.

Example Handler

With this setup, you can define your event handler as follows:

[[See Video to Reveal this Text or Code Snippet]]

Further Steps: Update Component State

Once you have the clicked component captured, you can easily perform operations such as setting its [selected] input variable to true or managing the states of other components.

Update the Selected State:

[[See Video to Reveal this Text or Code Snippet]]

Clear Previous Selections: Implement logic to reset other component states as needed.

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

Capturing a clicked component in Angular event handlers is made easy using template variables in conjunction with ngFor. This technique not only brings clarity to your code but also enhances your capability to interact with component instances effectively. Using this method, you can now successfully pass the full component and manage state seamlessly in your Angular applications.

So next time you encounter this challenge, remember this approach, and you'll be able to harness the full power of components in Angular!