# react/no-redundant-should-component-update

> Disallow `shouldComponentUpdate` in a class that extends `React.PureComponent`

`React.PureComponent` already decides when to render again by comparing the old and new props and state. If you write your own `shouldComponentUpdate`, it replaces that comparison, so extending `PureComponent` no longer does anything. Keep one of the two.

## Configure

Off by default. To turn it on:

```toml bunfig.toml
[lint.rules]
"react/no-redundant-should-component-update" = "error" # or "warn"
```

## Examples

Reported:

```jsx
class Price extends React.PureComponent {
  shouldComponentUpdate(nextProps) {
    return nextProps.amount !== this.props.amount;
  }

  render() {
    return <span>{this.props.amount}</span>;
  }
}
```

Not reported:

```jsx
class Price extends React.PureComponent {
  render() {
    return <span>{this.props.amount}</span>;
  }
}

class Total extends React.Component {
  shouldComponentUpdate(nextProps) {
    return nextProps.amount !== this.props.amount;
  }

  render() {
    return <strong>{this.props.amount}</strong>;
  }
}
```