Скачать или смотреть How to Use NgIf and NgSwitch in Angular for Conditional Rendering

Discover the most effective ways to handle conditional rendering in Angular templates using `NgIf` and `NgSwitch`. Learn when to implement logic in HTML or TypeScript.
---
This video is based on the question https://stackoverflow.com/q/76094207/ asked by the user 'Krktester23' ( https://stackoverflow.com/u/19607297/ ) and on the answer https://stackoverflow.com/a/76094254/ provided by the user 'Wandrille' ( https://stackoverflow.com/u/6664264/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Angular NgIf template with several conditions

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Understanding Angular Conditional Rendering: NgIf and NgSwitch

As a powerful framework for building dynamic web applications, Angular provides several tools for handling conditional rendering in templates. One common scenario developers face is needing to display data conditionally based on certain criteria. This guide will explore how to manage these conditions effectively, particularly focusing on the NgIf and NgSwitch directives in Angular.

The Problem

Suppose you have an object called vehicle with two properties: id and status. The vehicle.id can take one of three values: A, B, or C. Depending on the value of vehicle.id, you'll want to display different status messages in your HTML. For instance:

If vehicle.id is A, display 1.

If vehicle.id is B, display 2.

If vehicle.id is C, display 3.

This requires setting up conditional logic within your Angular template. You might wonder whether to implement this logic directly in the HTML or to handle it through TypeScript first.

The Solution: Using NgSwitch

Choosing the Right Tool

In Angular, if the condition is relatively simple and static, you can manage it using the ngSwitch directive. This approach enables a cleaner and more readable HTML structure. For more complex or dynamic conditions, it might be better to control the logic within your TypeScript file and use a function to determine the value to display.

Implementation in HTML

Here is an example of how to utilize NgSwitch in your Angular template:

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

Breakdown of the Code

[ngSwitch]="vehicle.id": This directive evaluates the vehicle.id and decides which content to render.

*ngSwitchCase="'A'": This syntax allows you to specify what should be displayed if the vehicle.id is A. The same applies for B and C.

Fallback Cases: You can also implement a *ngSwitchDefault case if you want to handle scenarios where vehicle.id does not match any of the specified cases.

Alternative Approach: Using TypeScript

If the logic gets more intricate and requires additional data processing, handling the value in your TypeScript file may be a more organized choice. Here’s how you might approach this:

Create a function in your component class that returns the appropriate status based on vehicle.id.

Call this function in your template to get the display value.

Sample TypeScript Code

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

Using TypeScript in HTML

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

Conclusion

When faced with conditional rendering in Angular, the choice between using NgSwitch in HTML versus a function in TypeScript depends largely on the complexity of your conditions. For straightforward cases, NgSwitch keeps your templates clean and intuitive. However, for more elaborate logic that may depend on multiple variables, handling it in TypeScript can provide better clarity and maintainability.

Explore your options and choose the one that best fits your application needs! Happy coding!