Angular - How to create custom structural directive?

Creating a custom structural directive in Angular allows you to modify the DOM based on certain conditions, extending the template syntax. Structural directives are identified by the asterisk (*) preceding the directive name in the HTML template. Let's go through the steps to create your own custom structural directive in Angular.

Step 1: Set up the Angular project: Ensure that you have Angular CLI installed. If not, you can install it using npm:

npm install -g @angular/cli

Create a new Angular project:

ng new custom-structural-directive-demo
cd custom-structural-directive-demo

Step 2: Generate the directive: Next, generate a new directive using Angular CLI:

ng generate directive customIf

This generates a new directive file named 'custom-if.directive.ts' in the 'src/app' folder.

Angular - An Introduction to Structural Directives in Angular

In post Directive in Angular, we tried to understand what is directive? In this post, we'll explore Structural Directives and understand how they enhance the functionality and flexibility of Angular applications.

What are Structural Directives?

Structural Directives in Angular are a type of directive that modify the layout and structure of the DOM by adding or removing elements based on conditions. Unlike Attribute Directives, which change an element's behavior or appearance, Structural Directives directly impact the DOM's structure. The most commonly used Structural Directives in Angular are 'ngIf', 'ngFor', and 'ngSwitch'.

1. ngIf: The 'ngIf' directive conditionally adds or removes an element from the DOM based on the evaluation of an expression. It proves particularly useful when you need to show or hide specific parts of your template depending on your application's state. Example:

<ng-container *ngIf="isLoggedIn">
  <p>Welcome, {{ username }}!</p>
</ng-container>

In this example, the '<p>' element will only be rendered if the 'isLoggedIn' variable is true.

Angular - Understanding ng-template and ng-content in Angular

In Angular, the features 'ng-template' and 'ng-content' are valuable tools that facilitate the creation of dynamic and reusable components. They significantly contribute to improving code modularity, reusability, and maintainability. Let's explore each of these features to comprehend their importance in Angular development.

1. ng-template:

In Angular, 'ng-template' is a directive that allows the definition of a template block within a component without immediate rendering. It serves as a placeholder for content that can be instantiated later, based on different conditions. Think of it as a blueprint for creating content that will only be activated when explicitly used.

Usage:

<ng-template #myTemplate>
  
</ng-template>

How to use ng-template:

The true power of 'ng-template' comes into play when used in conjunction with other Angular directives such as 'ngIf', 'ngFor', and custom structural directives. For example, with 'ngIf', you can conditionally render content based on specific logic:

Angular - Understanding Directives in Angular

Angular is a widely used front-end framework known for its ability to create dynamic web applications. One of its essential features is directives, enabling developers to extend HTML and build reusable components with customized behavior and functionality. In this post, we'll deep dive into what directives are, the various types available in Angular, and how to utilize them efficiently in your projects.

What are Directives?

In Angular, directives serve as markers on DOM elements, instructing Angular's compiler to attach specific behavior or functionality to those elements. They are instrumental in manipulating the DOM, adding or modifying elements, applying styles, handling events, and more. By using directives, you can extend HTML with your own custom attributes or tags, making your code more expressive and easier to maintain.

Types of Directives in Angular

Angular provides three primary types of directives:

1. Component Directives: Components are the most commonly used type of directive. They are essentially directives that come with an associated template. Components encapsulate the template, styles, and behavior of a specific part of the user interface, acting as reusable building blocks throughout your application.
2. Attribute Directives: Attribute directives modify the behavior or appearance of existing elements or components. They are used as attributes on elements and are denoted by square brackets, such as '[ngStyle]' or '[ngClass]'. Attribute directives are useful for applying conditional styles, enabling/disabling elements, or performing other transformations on elements.
3. Structural Directives: Structural directives modify the DOM's structure by adding or removing elements. They are also used as attributes but are denoted by an asterisk ('*') before the directive name. Some examples include '*ngIf', '*ngFor', and '*ngSwitch'. These directives are commonly employed for rendering lists, conditionally displaying content, and handling template rendering.

Angular - Utilizing the @ViewChild Decorator in Angular for Enhanced Component Interaction

Angular, a robust web application framework, offers developers a vast array of tools and features to boost productivity. One such feature is the @ViewChild decorator, which facilitates the access of child components, directives, or DOM elements within Angular components. In this article, we will explore the capabilities of @ViewChild and delve into its practical applications for interacting with child elements and components in your Angular applications.

Understanding @ViewChild:

The @ViewChild decorator enables developers to obtain references to child components, directives, or DOM elements residing within the template of a parent component. It grants access to properties and methods of the child component, facilitates interaction with the child directive, and allows direct manipulation of the DOM element.

Syntax: The syntax for implementing the @ViewChild decorator is as follows:

@ViewChild(selector, options) propertyName: Type;

1. The selector represents the CSS selector or component class used to identify the child element/component.
2. The options parameter is optional and allows for the specification of additional view query options.

Example 1: Accessing a Child Component

Let's consider a scenario where we have a parent component, ParentComponent, that includes a child component named ChildComponent. To access the child component from the parent component, we can utilize the @ViewChild decorator as illustrated below: