Can't use fetch inside yield call in redux saga

Question

I am making an api call and based on the response, I have to update the state. This is what I am doing.

function* testEndpointConnectivity(action){
    const { testConnectivityUri, rowItem } = action.payload
    const res=  yield call( fetch(testConnectivityUri).then(response => {
        //something here
        })
    )
   
   yield put({type: SOME_ACTION});
   
}

But this doesn't work. I get the error

 Error: call: argument fn is undefined

At first I tried putting the yield put in the catch and then of the response, but stackoverflow told me to use yield call.

Please help here.

Answer 1

It's not correct

if you check doc you will see the first argument it's function and then you can send arguments:

call(fn, ...args)

So, in your example correct variant must look like:

function* testEndpointConnectivity(action) {
    const { testConnectivityUri, rowItem } = action.payload;
    const response = yield call(fetch, testConnectivityUri);
    // and in generator you can wait your answer, you dont need use .then
    console.log("response", response);

    yield put({ type: SOME_ACTION });

}

 // this error mean, first argument in call function must be fetch
 Error: call: argument fn is undefined