shouldUpdate.md

shouldUpdate

Description

Higher-order component version of shouldComponentUpdate(). The test function accepts both the current props and the next props. If the return value of the defined expression is false, the component won't update.

API

shouldUpdate(
  expression : (props, nextProps) : boolean,
) : Function;

Example

import {
  linkEvent
} from 'inferno';

import {
  compose,
  withState,
  shouldUpdate
} from 'incompose';

const inc = (props) => {
  props.setCount(props.count += 1);
};

const dec = (props) => {
  props.setCount(props.count -= 1);
};

const Counter = (props) => (
  <div>
    <h1>count : {props.count}</h1>
    <button onClick={linkEvent(props, dec)}>-</button>
    <button onClick={linkEvent(props, inc)}>+</button>
  </div>
);

const withCounterState = withState('count', 'setCount', 1);

/**
 * should update prevents the component of re-render (shouldUpdate lifecycle hook)
 * you can compare current and next props and decide whether the component
 * should update or not. In this example, the counter just updates if
 * props.count is even.
 */
const withUpdatePolicy = shouldUpdate((props, nextProps) => (
  nextProps.count % 2 === 0
));

export default compose(
  withCounterState,
  withUpdatePolicy,
)(Counter);