checkClassInstance() — react Function Reference

Architecture documentation for the checkClassInstance() function in ReactFiberClassComponent.js from the react codebase.

Function javascript BabelCompiler Validation called by 1

Entity Profile

BabelCompiler→ Validation→ checkClassInstance() — react Function Reference

Dependency Diagram

graph TD
  3e3ed3f4_92fe_b808_59f1_ca6499a18813["checkClassInstance()"]
  3805476a_1924_0e35_fff7_6afad197a523["ReactFiberClassComponent.js"]
  3e3ed3f4_92fe_b808_59f1_ca6499a18813 -->|defined in| 3805476a_1924_0e35_fff7_6afad197a523
  3d21bb44_e12a_666f_ff91_4155c0f8d71b["mountClassInstance()"]
  3d21bb44_e12a_666f_ff91_4155c0f8d71b -->|calls| 3e3ed3f4_92fe_b808_59f1_ca6499a18813
  style 3e3ed3f4_92fe_b808_59f1_ca6499a18813 fill:#6366f1,stroke:#818cf8,color:#fff

Relationship Graph

Source Code

packages/react-reconciler/src/ReactFiberClassComponent.js lines 296–526

function checkClassInstance(workInProgress: Fiber, ctor: any, newProps: any) {
  const instance = workInProgress.stateNode;
  if (__DEV__) {
    const name = getComponentNameFromType(ctor) || 'Component';
    const renderPresent = instance.render;

    if (!renderPresent) {
      if (ctor.prototype && typeof ctor.prototype.render === 'function') {
        console.error(
          'No `render` method found on the %s ' +
            'instance: did you accidentally return an object from the constructor?',
          name,
        );
      } else {
        console.error(
          'No `render` method found on the %s ' +
            'instance: you may have forgotten to define `render`.',
          name,
        );
      }
    }

    if (
      instance.getInitialState &&
      !instance.getInitialState.isReactClassApproved &&
      !instance.state
    ) {
      console.error(
        'getInitialState was defined on %s, a plain JavaScript class. ' +
          'This is only supported for classes created using React.createClass. ' +
          'Did you mean to define a state property instead?',
        name,
      );
    }
    if (
      instance.getDefaultProps &&
      !instance.getDefaultProps.isReactClassApproved
    ) {
      console.error(
        'getDefaultProps was defined on %s, a plain JavaScript class. ' +
          'This is only supported for classes created using React.createClass. ' +
          'Use a static property to define defaultProps instead.',
        name,
      );
    }
    if (instance.contextType) {
      console.error(
        'contextType was defined as an instance property on %s. Use a static ' +
          'property to define contextType instead.',
        name,
      );
    }

    if (disableLegacyContext) {
      if (ctor.childContextTypes && !didWarnAboutChildContextTypes.has(ctor)) {
        didWarnAboutChildContextTypes.add(ctor);
        console.error(
          '%s uses the legacy childContextTypes API which was removed in React 19. ' +
            'Use React.createContext() instead. (https://react.dev/link/legacy-context)',
          name,
        );
      }
      if (ctor.contextTypes && !didWarnAboutContextTypes.has(ctor)) {
        didWarnAboutContextTypes.add(ctor);
        console.error(
          '%s uses the legacy contextTypes API which was removed in React 19. ' +
            'Use React.createContext() with static contextType instead. ' +
            '(https://react.dev/link/legacy-context)',
          name,
        );
      }
    } else {
      if (instance.contextTypes) {
        console.error(
          'contextTypes was defined as an instance property on %s. Use a static ' +
            'property to define contextTypes instead.',
          name,
        );
      }

      if (