Why cannot catch error in redux-saga generator? - reactjs

Question

Here is store/store.js
...
const initSagaMiddleware = createSagaMiddleware();
const middlewares = [initSagaMiddleware, fetchPhotosMiddleware, putPhotoMiddleware];
const middlewareEnhancer = applyMiddleware(...middlewares);
...
initSagaMiddleware.run(rootSaga);
export default store;
sagas/api-saga.js
export default function* rootSaga() {
yield all([
photoWatcher()
]);
}
function* photoWatcher() {
yield takeEvery(PUT_PHOTO, putPhotoWorker);
}
function* putPhotoWorker(action) {
try {
const payload = yield call(putPhoto, action.urlParams, action.body);
yield put({ type: PHOTO_UPDATED, payload });
} catch (err) {
yield put({ type: API_ERROR_PUT_PHOTO, payload: err });
}
}
and services/api.js
export function putPhoto(urlParams, body) {
return axios.put('/abc/' + urlParams.key + '/def/' + urlParams.id + '/edit', body)
.then(res => {
return res.data;
})
.catch(err => err);
}
My problem is: even when I get error from an api call, redux-saga putting PHOTO_UPDATED instead of API_ERROR_PUT_PHOTO. What am I doing wrong? How to catch error?

Answer 1

The problem is you are trying to catch the same error twice. Just remove the catch form the putPhoto function and it should work.
export function putPhoto(urlParams, body) {
return axios.put('/abc/' + urlParams.key + '/def/' + urlParams.id + '/edit', body)
.then(res => {
return res.data;
});
}

Answer 2

Both then and catch promises in putPhoto func were resulting in try statement. Because of that, I give up on try...catch, instead I'm using if...else statement now. Like this:
function* putPhotoWorker(action) {
const payload = yield call(putPhoto, action.urlParams, action.body);
if (isResponseTypeWhatIExpected) {
yield put({ type: PHOTO_UPDATED, payload });
} else {
yield put({ type: API_ERROR_PUT_PHOTO, payload });
}
}