Centralize thunk failure handling
Handle failures from selected async thunks in a slice without writing separate reducers for each rejected action.
Redux Toolkit · Function
isRejected
isRejected creates a type-safe matcher for rejected createAsyncThunk lifecycle actions. Optionally provide thunk action creators to limit which rejected actions match.
How it works
isRejected is a higher-order matcher for Redux Toolkit async-thunk lifecycle actions. Call it with optional thunk action creators to obtain a type guard that recognizes matching rejected actions, then use the returned matcher with addMatcher or middleware.
Syntax
isRejected(...actionCreators)Parameters
| Name | Type | Description |
|---|---|---|
actionCreators | AsyncThunk[] | Optional one or more action creators whose rejected lifecycle actions should match. |
Returns
A type guard function that returns true for matching rejected createAsyncThunk lifecycle actions.
Key points
- The utility belongs to Redux Toolkit's type-safe family of action matchers.
- Calling isRejected produces a predicate that also narrows the action type for TypeScript.
- It recognizes rejected actions generated by createAsyncThunk's promise lifecycle.
- Passing thunk action creators restricts matching to those creators.
- The same matcher can be configured for multiple thunk creators.
Example: Match a rejected thunk
import { configureStore, createAsyncThunk, createSlice, isRejected } from '@reduxjs/toolkit'
const loadUser = createAsyncThunk('user/load', async () => {
throw new Error('Network failure')
})
const slice = createSlice({
name: 'user',
initialState: { error: '' },
reducers: {},
extraReducers: (builder) => {
builder.addMatcher(isRejected(loadUser), (state, action) => {
state.error = action.error.message ?? 'Request failed'
})
},
})
const store = configureStore({ reducer: slice.reducer })
store.dispatch(loadUser())The matcher narrows rejected lifecycle actions from the selected thunk, allowing a reducer to handle its error.
When to use it
React to failures globally
Filter rejected async-thunk actions in middleware for logging, notifications, or telemetry.
Type-safe action inspection
Narrow an unknown Redux action before reading rejected-action fields in TypeScript.
Interview questions
QWhat does isRejected do?
isRejected accepts zero or more async-thunk action creators and returns a type guard for rejected lifecycle actions. With creators supplied, only rejected actions from those creators match.
Follow-up: How would you detect rejected actions carrying custom data? Use isRejectedWithValue, which checks for a rejected action with a payload.
QWhere is isRejected useful?
The returned matcher can be passed to builder.addMatcher or used as a predicate in middleware. A successful match narrows the action to a rejected async-thunk action.
Follow-up: How can matching be limited to one thunk? Pass that thunk's action creator to isRejected when creating the matcher.
QWhat kind of actions does it recognize?
It identifies rejected actions from the createAsyncThunk promise lifecycle. It is not a general test for arbitrary actions whose type happens to end in rejected.
Follow-up: What matcher covers every rejected action regardless of payload? isRejected matches rejected lifecycle actions, while isRejectedWithValue focuses on payload-bearing rejections.
Related
isPendingisFulfilledisRejectedWithValuecreateAsyncThunkaddMatcher