react runtime_error ai_generated true

TypeError: Cannot read properties of undefined (reading 'dispatch'). This error is located at: in ConsumerComponent (at App.js:10)

ID: react/context-not-provided

Also available as: JSON · Markdown · 中文
95%Fix Rate
88%Confidence
1Evidence
2023-04-10First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
[email protected] active — — —
[email protected] active — — —

Root Cause

A component tries to use useContext to access a context value, but it is not wrapped in the corresponding Provider component, so the context value is undefined.

generic

中文

组件尝试使用 useContext 访问上下文值，但它没有被相应的 Provider 组件包裹，因此上下文值为 undefined。

Official Documentation

https://reactjs.org/docs/context.html

Workarounds

  1. 95% success Wrap the component tree with the Provider: `<MyContext.Provider value={{ dispatch }}><ConsumerComponent /></MyContext.Provider>` 
    Wrap the component tree with the Provider: `<MyContext.Provider value={{ dispatch }}><ConsumerComponent /></MyContext.Provider>`
  2. 90% success If the Provider is already present but value is undefined, ensure the value prop is correctly passed: `<MyContext.Provider value={dispatch}>` (not just `value={}`) 
    If the Provider is already present but value is undefined, ensure the value prop is correctly passed: `<MyContext.Provider value={dispatch}>` (not just `value={}`)

中文步骤

  1. Wrap the component tree with the Provider: `<MyContext.Provider value={{ dispatch }}><ConsumerComponent /></MyContext.Provider>`
  2. If the Provider is already present but value is undefined, ensure the value prop is correctly passed: `<MyContext.Provider value={dispatch}>` (not just `value={}`)

Dead Ends

Common approaches that don't work:

  1. Importing the context directly and trying to use it as a value 75% fail

    The context object itself is not the value; it must be provided via a Provider.

  2. Adding a default value to createContext but not wrapping in Provider 50% fail

    The default value is only used when there is no Provider at all, but if the component is wrapped in a Provider without a value prop, the context is still undefined.

  3. Using useContext inside a class component 65% fail

    useContext is a hook and cannot be used in class components; use Context.Consumer instead.