react runtime_error ai_generated true

Error: The context value for 'MyContext' is undefined. Did you forget to wrap your component in a Provider with a value?

ID: react/context-value-undefined-reducer

Also available as: JSON · Markdown · 中文
90%Fix Rate
85%Confidence
1Evidence
2023-03-05First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
React 18.2.0 active — — —
React 19.0.0-beta.1 active — — —

Root Cause

A component tries to consume a context value that is undefined because the corresponding Provider is missing or does not provide a value prop.

generic

中文

组件尝试使用未定义的上下文值，因为对应的 Provider 缺失或未提供 value 属性。

Official Documentation

https://react.dev/reference/react/createContext#providing-context

Workarounds

  1. 95% success Ensure the component is wrapped in the correct Provider with a value prop. Example: <MyContext.Provider value={someValue}><ChildComponent /></MyContext.Provider> 
    Ensure the component is wrapped in the correct Provider with a value prop. Example: <MyContext.Provider value={someValue}><ChildComponent /></MyContext.Provider>
  2. 85% success Check the context creation file to ensure the context is exported and imported correctly. Use named exports to avoid confusion. 
    Check the context creation file to ensure the context is exported and imported correctly. Use named exports to avoid confusion.
  3. 90% success If using useReducer, pass the dispatch as part of the context value: const [state, dispatch] = useReducer(reducer, initialState); <MyContext.Provider value={{ state, dispatch }}>...</MyContext.Provider> 
    If using useReducer, pass the dispatch as part of the context value: const [state, dispatch] = useReducer(reducer, initialState); <MyContext.Provider value={{ state, dispatch }}>...</MyContext.Provider>

中文步骤

  1. Ensure the component is wrapped in the correct Provider with a value prop. Example: <MyContext.Provider value={someValue}><ChildComponent /></MyContext.Provider>
  2. Check the context creation file to ensure the context is exported and imported correctly. Use named exports to avoid confusion.
  3. If using useReducer, pass the dispatch as part of the context value: const [state, dispatch] = useReducer(reducer, initialState); <MyContext.Provider value={{ state, dispatch }}>...</MyContext.Provider>

Dead Ends

Common approaches that don't work:

  1. 70% fail

    The default value is used only if there is no Provider; if a Provider exists without a value, it still passes undefined.

  2. 80% fail

    This causes a mismatch between the context used in the Provider and the consumer.

  3. 90% fail

    Without a value prop, the Provider passes undefined, which is still undefined.