How to apply filters to *ngFor?

How to Apply Filters to *ngFor? 💡✨

So you want to apply filters to your *ngFor loop in Angular 2? You're in the right place! In Angular 2, instead of using filters like in Angular 1, pipes are used in conjunction with *ngFor to filter the results. Although the documentation may be a bit unclear, don't worry – I've got you covered! In this guide, I'll walk you through the process of applying filters to *ngFor and provide easy solutions to common issues you may face. Let's dive in! 🚀

The Context 📜

Before we jump into the solutions, let's quickly understand the context:

<div *ng-for="let item of itemsList" *ng-if="condition(item)"></div>

In the above example, we want to iterate over itemsList using *ngFor, but we also want to apply a condition to filter the results. To achieve this, we need to use pipes. Let's see how! 💪

Solution 1: Using the Built-in Filter Pipe 🧰

Angular 2 provides a built-in pipe called filter that you can use to apply filters to *ngFor. Here's how you can do it:

<div *ng-for="let item of itemsList | filter: condition"></div>

In the above code snippet, we've added | filter: condition after itemsList. This tells Angular 2 to apply the filter pipe with the condition as the filter criteria. Pretty neat, right?

Solution 2: Creating a Custom Filter Pipe 🛠️

If the built-in filter pipe doesn't fulfill your needs, you can create a custom filter pipe. Creating a custom pipe allows you to have full control over the filtering logic. Let me show you how it's done:

1. Create a new file called filter.pipe.ts and add the following code:

import { Pipe, PipeTransform } from '@angular/core';

@Pipe({
  name: 'filter'
})
export class FilterPipe implements PipeTransform {
  transform(items: any[], condition: any): any {
    // Filtering logic goes here
  }
}

1. In your component file, import and declare the custom pipe:

import { FilterPipe } from './filter.pipe';

@Component({
  // Component metadata goes here
})
export class YourComponent {
  constructor(private filterPipe: FilterPipe) {}
  // Rest of your component code
}

1. Finally, implement the filtering logic in the transform method in filter.pipe.ts:

transform(items: any[], condition: any): any {
  // Filtering logic goes here
  return items.filter(item => condition(item));
}

Now you can use your custom filter pipe in the template:

<div *ng-for="let item of itemsList | filter: condition"></div>

Conclusion 🎉

Congratulations! You've learned two ways to apply filters to *ngFor in Angular 2. You can either use the built-in filter pipe or create a custom filter pipe to have full control over the filtering logic. Now it's your turn to give it a try! If you encounter any issues or have any questions, feel free to leave a comment below. Happy coding! 💻✨

Liked this guide? Don't forget to share it with your fellow developers! If you found it helpful, be sure to leave a comment and let me know your thoughts. I'd love to hear your feedback and engage in a discussion with the community. Until next time, happy filtering! 👋