How to get JSON data from fetch (react-native)

Question

I'm writing small app for iPhone using react native. I'm trying to fetch JSON data from a website using fetch. Like in the example:

   function status(response) {
  if (response.status >= 200 && response.status < 300) {
    return response
  }
  throw new Error(response.statusText)
}

function json(response) {
  return response.json()
}


fetch('/users', {
  method: 'post',
  headers: {
    'Accept': 'application/json',
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    name: 'Hubot',
    login: 'hubot',
  })
}).then(status)
  .then(json)
  .then(function(json) {
    console.log('request succeeded with json response', json)
  }).catch(function(error) {
    console.log('request failed', error)
  })

Everything works fine but I need to use that data later. When I try to assign it to some variable in json function, I get "Request error" and after that get the data (correctly). What's the best practise to get that data and have it in some variable to use it later?

coderzzz18 · Accepted Answer · 2016-09-29 07:49:52Z

I did it like this. I displayed the response on console. You can store the response data in your state variable or in local storage as you want.

  doSignUp() {

     console.log("inside post api");
     fetch('your API URL', {
     method: 'POST',
     headers: {
                  'Accept': 'application/json',
                  'Content-Type': 'application/json',

                },


      body: JSON.stringify({
      password: this.state.password,
      email:this.state.email,
      name: this.state.firstname,
      last_name :this.state.last_name,
      mobile:this.state.mobile,
      ssn:"2222222"

     })
      }).then((response) => response.json())
        .then((responseData) => {
                                 console.log("inside responsejson");
                                 console.log('response object:',responseData)

         }).done();
     }

Niccolò Passolunghi · Accepted Answer · 2015-05-06 07:31:13Z

6

You can create a variable in the component's constructor:

constructor(props) {
    super(props);
    this.state = {
       jsonData: ''
    }
}

Then you update this variable when you needed:

 .then((responseData) => {
    this.setState({
      jsonData: responseData
    });
  })

answered May 6, 2015 at 7:31

Niccolò Passolunghi

6,0242 gold badges27 silver badges34 bronze badges

2 Comments

Kevin Zhao Over a year ago

in the fetch method, you usually have two thens like this:

.then((response) => {     response.text();     console.log(response);   })   .then((responseText) => {     console.log(responseText);   })   .catch((error) => {     console.warn(error);   })   .done();

I was wondering what does each of the two then returns and why is it organized that way? how do they work?

vignesh Over a year ago

@KevinZhao : The 2 then gets executed sequentially, 1st then is to get text from the response object and the 2nd one is to print text value.

Mahdi Bashirpour · Accepted Answer · 2020-07-25 05:05:59Z

2

Firstly, as you know, each request returns a header and a body

When we use fetch a default response that is headers request. If we need to body of request, that's enough response.json()

return fetch(url,{
  method: 'POST',//GET and ...
  headers:{
      Accept: 'application/json',
      'Content-Type': 'application/json',
  },
  body: JSON.stringify({
      elm: "elm" //is fake
  })
 })
 .then((response)=>response.json()) //   <------ this line 
 .then((response)=>{
   return response ;
 });

And if the body of your request is html dom Just use this response.text()

And if you want to return your header no need to do anything, Just add this line .then((response)=>response.json())

edited Jul 25, 2020 at 5:05

answered Apr 12, 2018 at 20:48

Mahdi Bashirpour

19k17 gold badges134 silver badges154 bronze badges

1 Comment

Matheus Cabral Over a year ago

Hi, if i need to put a token, where i put then?

Mounir Dhahri · Accepted Answer · 2016-08-03 17:26:48Z

0

In my case, i used a sails.js with passport local but it's very similar to any other node.js framework, to catch these variables I used for signin a function(req,res) where variables where stored in req.body. In your case req.body.name will contain 'Hubot' and req.body.login will contain 'hubot'.Response will be sent using res.send. check the node.js documentation for more details.

answered Aug 3, 2016 at 17:26

Mounir Dhahri

232 bronze badges

Comments

Ryosuke Hujisawa · Accepted Answer · 2018-12-13 05:31:17Z

0

Me works like this

This is button

<Button onPress={this._onPressButton} accessibilityLabel="tap!!!" />

This is action

  _onPressButton() {

  return fetch('https://facebook.github.io/react-native/movies.json')
    .then((response) => response.json())
    .then((responseJson) => {
      console.log(responseJson.movies);
    })
    .catch((error) => {
      console.error(error);
    });

  }

result

[14:30:19] Array [
[14:30:19]   Object {
[14:30:19]     "id": "1",
[14:30:19]     "releaseYear": "1977",
[14:30:19]     "title": "Star Wars",
[14:30:19]   },
[14:30:19]   Object {
[14:30:19]     "id": "2",
[14:30:19]     "releaseYear": "1985",
[14:30:19]     "title": "Back to the Future",
[14:30:19]   },
[14:30:19]   Object {
[14:30:19]     "id": "3",
[14:30:19]     "releaseYear": "1999",
[14:30:19]     "title": "The Matrix",
[14:30:19]   },
[14:30:19]   Object {
[14:30:19]     "id": "4",
[14:30:19]     "releaseYear": "2010",
[14:30:19]     "title": "Inception",
[14:30:19]   },
[14:30:19]   Object {
[14:30:19]     "id": "5",
[14:30:19]     "releaseYear": "2014",
[14:30:19]     "title": "Interstellar",
[14:30:19]   },
[14:30:19] ]
[14:30:19] Array [
[14:30:19]   Object {
[14:30:19]     "id": "1",
[14:30:19]     "releaseYear": "1977",
[14:30:19]     "title": "Star Wars",
[14:30:19]   },
[14:30:19]   Object {
[14:30:19]     "id": "2",
[14:30:19]     "releaseYear": "1985",
[14:30:19]     "title": "Back to the Future",
[14:30:19]   },
[14:30:19]   Object {
[14:30:19]     "id": "3",
[14:30:19]     "releaseYear": "1999",
[14:30:19]     "title": "The Matrix",
[14:30:19]   },
[14:30:19]   Object {
[14:30:19]     "id": "4",
[14:30:19]     "releaseYear": "2010",
[14:30:19]     "title": "Inception",
[14:30:19]   },
[14:30:19]   Object {
[14:30:19]     "id": "5",
[14:30:19]     "releaseYear": "2014",
[14:30:19]     "title": "Interstellar",
[14:30:19]   },
[14:30:19] ]

answered Dec 13, 2018 at 5:31

Ryosuke Hujisawa

2,8721 gold badge19 silver badges18 bronze badges

3 Comments

Ryosuke Hujisawa Over a year ago

Ryosuke Hujisawa Over a year ago

☝︎I need make button like this sorry

Ryosuke Hujisawa Over a year ago

And I think no work local and http host like that shit "localhost:3000/api/signup"

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