Fetch react native get data out of the function

Question

I'm trying to make a fetch function that return the data like a classic function. like this :

function fetchGetData(idUser){
        fetch('url?idU='+idUser)
        .then((response)=>console.log(response))
        .then((responseText)=>{
            if(responseText.result!='true'){
                console.log(responseText)
             return parseInt(responseText) // return the data (a number for me)
            }
            else {
              return 0 ; 
            }
        });
    }

then I want to use the function like this : var data = fetchGetData(id); I'm new on react, I don't know if its possible. In my context, i can't use states to save it in the function. Any ideas? Thank you

Have you determined if response from server is `JSON` or plain text? — guest271314, Apr 23 '17 at 07:15
the response is plain text. i tried your code but it didnt works for me :( — Meyes, Apr 23 '17 at 07:27
Can you describe "didnt works"? Have you tried linked jsfiddle https://jsfiddle.net/bvcdyj4k/? — guest271314, Apr 23 '17 at 07:31

score 1 · Answer 1 · edited Jun 20 '20 at 09:12

1

Because you want to asgin response of the request to a vaiable like a sync function response (var data = fetchGetData(id);), It's better to use async/await for this case. It's your rewritten fetchGetData:

async function fetchGetData(idUser){
  try {
    let response = await fetch('url?idU='+idUser);
    console.log(response);
    let responseText = await response; // are you sure it's not response.json();?
    if(responseText.result!='true'){
      console.log(responseText);
      return parseInt(responseText) // return the data (a number for me)
    } else {
      return 0 ; 
    }
  } catch(error) {
    console.error(error);
  }
}

Now you can assign it's returned value by calling the function:

var data = await fetchGetData(id);

In this way, you are using async actions link sync actions.

edited Jun 20 '20 at 09:12

Community

1
1

answered Apr 23 '17 at 06:01

Meysam Izadmehr

3,103
17
25

_"It's better to use async/await for this case."_ Can you define "better"? Is `response` a `javascript` object or text? – guest271314 Apr 23 '17 at 06:03
Better is because how response assigned (`var data = fetchGetData(id);`). – Meysam Izadmehr Apr 23 '17 at 06:10
That is not the definition of "better". The approaches are functionally equivalent [Implementing coroutine control flow in JavaScript](http://stackoverflow.com/questions/43547606/implementing-coroutine-control-flow-in-javascript) – guest271314 Apr 23 '17 at 06:12
thanks for your responses, the fetch call a php function that return a number. I dont know what response type is, i just wanna get that number in a variable out of the fetch function. I can see it with a console log inside of the function but i cant outside – Meyes Apr 23 '17 at 06:26
Note, the `responseText` cannot be a `javascript` object and plain text at the same time. – guest271314 Apr 23 '17 at 07:33

score 0 · Answer 2 · answered Apr 23 '17 at 05:57

If expected response is JSON, chain .json() to response to return javascript object, else use .text() to return response as plain text

function fetchGetData(idUser) {
  return fetch('url?idU=' + idUser) // note `return` fetch from function call
    .then(response => {
      return response.text() // if `response` is `JSON` use `.json()` here
    })
    .then(responseText => {
    //  if (responseText.result != 'true') { // is expected response `JSON` or text?
        console.log(responseText);
        return parseInt(responseText) // return the data (a number for me)
    //  } else {
    //    return 0;
    //  }
    })
    .catch(err => Promise.reject(err))
}

thank's for your response, i want to return a number in this fonction, basically a text. my fetch call a php fonction that returns a number. i juste want to get that number. — Meyes, Apr 23 '17 at 06:18
`javascript` at Answer should return expected result https://jsfiddle.net/bvcdyj4k/ — guest271314, Apr 23 '17 at 06:23

score 0 · Answer 3 · answered Jul 17 '17 at 04:18

0

I had a similar problem.. use _bodyText properties

function fetchGetData(idUser){
        fetch('url?idU='+idUser)
        .then((response)=>{console.log(response._bodyText)
              return parseInt(response._bodyText)})
        );
    }

answered Jul 17 '17 at 04:18

ViTUu

1,204
11
21

Fetch react native get data out of the function

3 Answers3