createSlice

CreateSlice is a function in Redux Toolkit that creates a slice of the Redux state by bundling reducers and action creators in a single configuration object. It automates the generation of action types and action creators, reducing boilerplate compared with traditional Redux setups.

Usage: You call createSlice with an object that includes name, initialState, and reducers, with optional extraReducers. The reducers object maps case names to reducer functions (state, action) => newState. Inside these reducers you can write code that mutates state directly because Immer handles immutability behind the scenes. The slice name prefixes action types, producing strings like 'sliceName/caseName'.

extraReducers allows handling actions defined outside the slice. It can be provided as an object map of action types to reducers or as a builder callback using addCase, addMatcher, and addDefaultCase.

Return value: the call yields an object containing a reducer function to be added to the store and an actions object containing action creators corresponding to each reducer key. Typical usage is to export the action creators and the reducer for use with configureStore.

Benefits: reduces boilerplate, ensures consistent action type naming, and works well with TypeScript and createAsyncThunk scenarios. The generated actions and reducer integrate smoothly with the store setup, providing a concise and predictable pattern for managing slice-specific state.