Understanding the 'ngSwitch' Directive in Angular

The 'ngSwitch' directive in Angular plays an important role in giving the conditional rendering capability to our templates. Before diving into how it works, it's crucial to understand why it is essential.

In any application development, there are situations where we want to display different templates or components based on certain conditions. For instance, you might want to show different screens based on user role, or different elements based on the user's choices. Handling such scenarios directly in the code can lead to complex and difficult to maintain logic.

That's where 'ngSwitch' comes into play, making it elegant to handle such situations. 'ngSwitch' is a built-in directive provided by the Angular framework that acts like a switch statement in JavaScript. It is used for adding/removing DOM elements by checking a condition.

Here's a basic example of an 'ngSwitch' directive:

<div [ngSwitch]="expression">
  <div *ngSwitchCase="'value1'"> 
      // Html to render when expression is 'value1'
  </div>
  <div *ngSwitchCase="'value2'"> 
      // Html to render when expression is 'value2'
  </div>
  <div *ngSwitchDefault> 
    // Html to render when none of the case value matches the expression
  </div>
</div>

In this example, depending on the value of the 'expression,' one of the 'ngSwitchCase' sections will be displayed. If none match, then the section marked by 'ngSwitchDefault' will be shown.

Best Practices & Insights

While working with 'ngSwitch' directive, one must bear a few things in mind:

• Always consider including an '*ngSwitchDefault' case to handle unexpected values. This makes your code robust against possible edge cases.
• Be mindful of the performance implications. Each time the expression changes, Angular will destroy and recreate the matching elements. Hence, avoid heavy computations in the binding expression.
• 'ngSwitch' should be chosen over 'ngIf' when there are three or more options to be rendered. This enhances code readability and maintainability.

In summary, the 'ngSwitch' directive is a powerful tool in Angular that can make your templates more dynamic and reactive to conditions. This helps in creating complex UIs in a more manageable way.