Javascript: Expected "this" in class method react native

[vzhen]

In react native navigator component. I move renderScene attr out to a class method. It check if route.id match and return component. It forces me to use "this" but i don't think i need it. I am on phone can't show code. Any suggestion or just simply // eslint-disable?

[ljharb]

I'd need to see code to be certain.

Basically, outside of interface things a framework requires (like React component methods), things should only be instance methods if they need this - otherwise they should be static methods, or closed-over functions.

[vzhen]

@ljharb code added

  // Warning here, expected "this" to be used in class method 'renderScene'
  renderScene(route, navigator) {
    switch (route.id) {
      case 'Home':
        return <Home />;
      case 'Cart':
        return <Cart />;
      case 'Settings':
        return <Settings />;
      default:
        return <Main navigator={navigator} {...route.passProps} />;
    }
  }

  render() {
    return (
      <Navigator
        initialRoute={{ id: 'App' }}
        renderScene={this.renderScene}
      />
    );
  }

[ljharb]

That seems like a great use case for a separate function or a static method. Is there any reason it needs to be an instance method?

[ljharb]

Put another way - is that a special method in React Native? If so, it belongs on the instance - if not, it doesn't.

[vzhen]

It doesn't need to be instance and not a special method too.
I made it to static method and now works fine but 1 more question.

In es6 instead of calling ClassName.renderScene within class. Any other keyword i can use?
this.renderScene doesn't work

Anyway, this is fixed. Thanks again.

[ljharb]

Using the hardcoded class name is the most reliable.

[nathanhleung]

To answer your question @vzhen you can also use this.constructor.renderScene.

What are your thoughts on this approach @ljharb - is it ever used @airbnb?

[ljharb]

You should never use the constructor property; it's not reliably present nor is it robust against tampering. Since there's no language keyword to mean "the current class", you should simply hardcode it.

[nathanhleung]

I recently came across the new.target property which reminded me of this discussion - is the new.target property be robust enough to be used to refer to the current class?

[ljharb]

It can't be fully polyfilled or transpiled, so no, it's not robust enough. Separately, it would only work inside the constructor itself.