chain promise to function

Question

I have a function

const func = () => server.insertPatientSurveyQuestionToDataBase(Store.getPatientID(), SurveyNumber, Store.getPatientQuestion())

that is called.

after this, there is a function:

const promise = 
  server.GetPatientHistoryData(Store.getPatientID())
    .then(
      response => Dispatcher.dispatch({
        actionType: Constants.CHANGE_PATIENT_HISTORY,
        payload:response}))

    .catch(error => {console.log(error)});

I do this, which i believe should work:

func().then(response => promise())

but it returns a cannot read property then of undefined. I was under the impression this could work. How do I chain a function to a promise?

Answer 1

It causes this error because func doesn't return a promise. If this part is a promise:

server.insertPatientSurveyQuestionToDataBase(Store.getPatientID(), SurveyNumber, Store.getPatientQuestion());

You need to return it inside of func:

const func = () => {
    return server.insertPatientSurveyQuestionToDataBase(Store.getPatientID(), SurveyNumber, Store.getPatientQuestion());
};

Then you can safely use it like this:

func().then(response => promise());