CODEWITHSUNDEEP
javascriptreactjsclass
stackjlei
stackjlei

Reputation: 10035

Why do propTypes live on the class but not other methods?

I read that using static for propTypes puts the it on the class instead of the instance of the React component. I don't get the difference between putting something on the class vs. the instance though. Why is propTypes on the class but not methods like render and componentDidMount, or other custom made methods inside the component?

Upvotes: 0

Views: 45

Answers (1)

caesay
caesay

Reputation: 17223

It's for the same reason as the keyword static. This is un-changing static metadata that helps describe your class. It can be accessed without needing to instantiate your class (accessed without calling the constructor).

class example extends Component {
    static propTypes = {
        something: PropTypes.object,
    }

    static displayName = "ExampleDisplay";

    render() {
        return <div />;
    }
}

// I can access static properties here directly
var types = example.propTypes; 
var name = example.displayName;


// I can NOT access the render method without instantiating the class.
var instance = new example(); // <- this calls the constructor and creates an instance.
var renderFn = instance.render;

The question is really: why should I need to create the class just to read the propTypes or displayName? you shouldn't need to. that's why you have static.

Upvotes: 1

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