Using Classes to Create Components

Hello, students! In the previous topic, we learned about component hierarchy.

In this class, we will learn about using classes to create components.

What are Classes in React?

Classes are a way to organize code and data in React.

They can be used to create more complex and reusable components.

Advantages of Using Classes to Create Components

Using classes to create components offers several advantages, including:

• Organization: Classes can help organize the code and data of a component logically.
• Reuse: Classes can be reused in different parts of the user interface.
• Testability: Classes can be tested individually, facilitating the debugging of issues.

How to Create Components Using Classes

To create a component using classes, we need to define a class that inherits from React.Component.

The class must have a render() method that returns the JSX code that will be rendered by the component.

Additionally, the class can have other methods and properties to define the behavior and data of the component.

Example of a Component Using Classes

Let’s see an example of how to create a component using classes:

class MyComponent extends React.Component {
  render() {
    return (
      <div>
        <h1>My Header</h1>
      </div>
    );
  }
}

This component renders a header with the message “My Header.”

Component Properties

Classes of components can have properties to receive data from the outside.

These properties are defined in the class declaration using the propTypes modifier.

Example of a Component with Properties

class MyComponent extends React.Component {
  static propTypes = {
    title: PropTypes.string.isRequired,
  };

  render() {
    return (
      <div>
        <h1>{this.props.title}</h1>
      </div>
    );
  }
}

This component receives a property called title, which must be a string.

Component State

Classes of components can have state to store data that changes during the component’s lifecycle.

The state is defined in the class declaration using the state modifier.

Example of a Component with State

class MyComponent extends React.Component {
  state = {
    count: 0,
  };

  incrementCount = () => {
    this.setState({
      count: this.state.count + 1,
    });
  };

  render() {
    return (
      <div>
        <h1>The count is {this.state.count}</h1>
        <button onClick={this.incrementCount}>Increment</button>
      </div>
    );
  }
}

This component has a state called count, which is initialized with the value 0.

The component also has a method called incrementCount(), which increments the value of the count state by 1.

Conclusion

Classes are a powerful way to create components in React.

They can be used to create more complex and reusable components.

If you have any questions, leave them in the comments. So, we can go to the next class.