What are the problems of using render props with pure components?
Interviewer Expectations for this Question
01
Core Competency
Assesses fundamental understanding of React conventions, runtime behavior, and memory/performance considerations.
02
Evaluation Criteria
Hiring managers look for precision, avoidance of ambiguous jargon, and ability to explain trade-offs under real production conditions.
Comprehensive Model Answer
Verified Solution
If you create a function inside a render method, it negates the purpose of pure component. Because the shallow prop comparison will always return false for new props, and each render in this case will generate a new value for the render prop. You can solve this issue by defining the render function as instance method.
class Mouse extends React.PureComponent {
render() {
// BAD: a new arrow function reference is created on every render,
// so PureComponent's shallow comparison always sees "new" props
return <MouseTracker render={(mouse) => <Cat mouse={mouse} />} />;
}
}
class MouseWithCat extends React.PureComponent {
// GOOD: defined once as an instance method/class property, so the
// reference stays stable across renders
renderTheCat = (mouse) => <Cat mouse={mouse} />;
render() {
return <MouseTracker render={this.renderTheCat} />;
}
}
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