rn-fetch-blob

react-native-fetch-blob

A module provides upload, download, and files access API. Supports file stream read/write for process large files.

Why do we need this

At this moment, React Native does not support Blob object yet, so if you’re going to send/receive binary data via fetch API, that might not work as you expect. See [fetch] Does fetch with blob() marshal data across the bridge?.

Hence you may getting into trouble in some use cases. For example, displaying an image on image server but the server requires a specific field(such as “Authorization”) in headers or body, so you can’t just pass the image uri to Image component because that will probably returns a 401 response. With help of this module, you can send a HTTP request with any headers, and decide how to handle the response/reqeust data. The response data can be just simply converted into BASE64 string, or store to a file directly so that you can read it by file stream or use it’s path.

This module is designed to be a substitution of blob, there’s a set of file access API including basic CRUD method, and file stream reader/writer. Also it has a special fetch implementation that supports binary request/response body.

Pre v0.5.0 Users

This update is backward-compatible generally you don’t have to change existing code unless you’re going to use new APIs. In latest version (v0.5.0), new APIs can either upload or download files simply using a file path. It’s much more memory efficent in some use case. We’ve also introduced fs APIs for access files, and file stream API that helps you read/write files (especially for large ones), see Examples bellow. This module implements native methods, supports both Android (uses awesome native library AsyncHttpClient) and IOS.

TOC

• Installation
• Guide
  • Download file
  • Upload file
  • Multipart/form upload
  • Upload/Download progress
  • Android Media Scanner, and Downloads App Support
  • File access
  • File stream
  • Manage cached files
• API
  • config
  • fetch
  • session
  • base64
  • fs
• Development

Installation

Install package from npm

npm install --save react-native-fetch-blob

Link package using rnpm

rnpm link

Grant Permission to External storage for Android 5.0 or lower

Mechanism about granting Android permissions has slightly different since Android 6.0 released, please refer to Officail Document.

If you’re going to access external storage (say, SD card storage) for Android 5.0 (or lower) devices, you might have to add the following line to AndroidManifetst.xml.

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.rnfetchblobtest"
    android:versionCode="1"
    android:versionName="1.0">

    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW"/>
+   <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />                                               
+   <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />                                              

    ...

Grant Access Permission for Android 6.0

Beginning in Android 6.0 (API level 23), users grant permissions to apps while the app is running, not when they install the app. So adding permissions in AndroidManifest.xml won’t work in Android 6.0 devices. To grant permissions in runtime, you might use modules like react-native-android-permissions.

Guide

import RNFetchBlob from 'react-native-fetch-blob'

Download example : Fetch files that needs authorization token

// send http request in a new thread (using native code)
RNFetchBlob.fetch('GET', 'http://www.example.com/images/img1.png', {
    Authorization : 'Bearer access-token...',
    // more headers  ..
  })
  // when response status code is 200
  .then((res) => {
    // the conversion is done in native code
    let base64Str = res.base64()
    // the following conversions are done in js, it's SYNC
    let text = res.text()
    let json = res.json()

  })
  // Status code is not 200
  .catch((errorMessage, statusCode) => {
    // error handling
  })

Download to storage directly

The simplest way is give a fileCach option to config, and set it to true. This will let the incoming response data stored in a temporary path wihout any file extension.

These files won’t be removed automatically, please refer to Cache File Management

RNFetchBlob
  .config({
    // add this option that makes response data to be stored as a file,
    // this is much more performant.
    fileCache : true,
  })
  .fetch('GET', 'http://www.example.com/file/example.zip', {
    some headers ..
  })
  .then((res) => {
    // the temp file path
    console.log('The file saved to ', res.path())
  })

Set Temp File Extension

Sometimes you might need a file extension for some reason. For instance, when using file path as source of Image component, the path should end with something like .png or .jpg, you can do this by add appendExt option to config.

RNFetchBlob
  .config({
    fileCache : true,
    // by adding this option, the temp files will have a file extension
    appendExt : 'png'
  })
  .fetch('GET', 'http://www.example.com/file/example.zip', {
    some headers ..
  })
  .then((res) => {
    // the temp file path with file extension `png`
    console.log('The file saved to ', res.path())
    // Beware that when using a file path as Image source on Android,
    // you must prepend "file://"" before the file path
    imageView = <Image source={{ uri : Platform.OS === 'android' ? 'file://' : '' + res.path() }}/>
  })

Use Specific File Path

If you prefer a specific path rather than random generated one, you can use path option. We’ve added a constant dirs in v0.5.0 that contains several common used directories.

let dirs = RNFetchBlob.fs.dirs
RNFetchBlob
.config({
  // response data will be saved to this path if it has access right.
  path : dirs.DocumentDir + '/path-to-file.anything'
})
.fetch('GET', 'http://www.example.com/file/example.zip', {
  //some headers ..
})
.then((res) => {
  // the path should be dirs.DocumentDir + 'path-to-file.anything'
  console.log('The file saved to ', res.path())
})

These files won’t be removed automatically, please refer to Cache File Management

Upload example : Dropbox files-upload API

react-native-fetch-blob will convert the base64 string in body to binary format using native API, this process will be done in a new thread, so it’s async.

RNFetchBlob.fetch('POST', 'https://content.dropboxapi.com/2/files/upload', {
    Authorization : "Bearer access-token...",
    'Dropbox-API-Arg': JSON.stringify({
      path : '/img-from-react-native.png',
      mode : 'add',
      autorename : true,
      mute : false
    }),
    'Content-Type' : 'application/octet-stream',
    // here's the body you're going to send, should be a BASE64 encoded string
    // (you can use "base64" APIs to make one).
    // The data will be converted to "byte array"(say, blob) before request sent.  
  }, base64ImageString)
  .then((res) => {
    console.log(res.text())
  })
  .catch((err) => {
    // error handling ..
  })

Upload a file from storage

If you’re going to use a file request body, just wrap the path with wrap API.

RNFetchBlob.fetch('POST', 'https://content.dropboxapi.com/2/files/upload', {
    // dropbox upload headers
    Authorization : "Bearer access-token...",
    'Dropbox-API-Arg': JSON.stringify({
      path : '/img-from-react-native.png',
      mode : 'add',
      autorename : true,
      mute : false
    }),
    'Content-Type' : 'application/octet-stream',
    // Change BASE64 encoded data to a file path with prefix `RNFetchBlob-file://`.
    // Or simply wrap the file path with RNFetchBlob.wrap().
  }, RNFetchBlob.wrap(PATH_TO_THE_FILE))
  .then((res) => {
    console.log(res.text())
  })
  .catch((err) => {
    // error handling ..
  })

Multipart/form-data example : Post form data with file and data

In version >= 0.3.0 you can also post files with form data, just put an array in body, with elements have property name, data, and filename(optional).

Elements have property filename will be transformed into binary format, otherwise it turns into utf8 string.

  RNFetchBlob.fetch('POST', 'http://www.example.com/upload-form', {
    Authorization : "Bearer access-token",
    otherHeader : "foo",
    'Content-Type' : 'multipart/form-data',
  }, [
    // element with property `filename` will be transformed into `file` in form data
    { name : 'avatar', filename : 'avatar.png', data: binaryDataInBase64},
    // elements without property `filename` will be sent as plain text
    { name : 'name', data : 'user'},
    { name : 'info', data : JSON.stringify({
      mail : 'example@example.com',
      tel : '12345678'
    })},
  ]).then((resp) => {
    // ...
  }).catch((err) => {
    // ...
  })

What if you want to upload a file in some field ? Just like upload a file from storage example, wrap data by wrap API (this feature is only available for version >= v0.5.0)

  RNFetchBlob.fetch('POST', 'http://www.example.com/upload-form', {
    Authorization : "Bearer access-token",
    otherHeader : "foo",
    // this is required, otherwise it won't be process as a multipart/form-data request
    'Content-Type' : 'multipart/form-data',
  }, [
    // append field data from file path
    {
      name : 'avatar',
      filename : 'avatar.png',
      // Change BASE64 encoded data to a file path with prefix `RNFetchBlob-file://`.
      // Or simply wrap the file path with RNFetchBlob.wrap().
      data: RNFetchBlob.wrap(PATH_TO_THE_FILE)
    },
    // elements without property `filename` will be sent as plain text
    { name : 'name', data : 'user'},
    { name : 'info', data : JSON.stringify({
      mail : 'example@example.com',
      tel : '12345678'
    })},
  ]).then((resp) => {
    // ...
  }).catch((err) => {
    // ...
  })

Upload/Download progress

In version >= 0.4.2 it is possible to know the upload/download progress.

  RNFetchBlob.fetch('POST', 'http://www.example.com/upload', {
      ... some headers,
      'Content-Type' : 'octet-stream'
    }, base64DataString)
    .progress((received, total) => {
        console.log('progress', received / total)
    })
    .then((resp) => {
      // ...
    })
    .catch((err) => {
      // ...
    })

Android Media Scanner, and Downloads App Support

If you want to make a file in External Storage becomes visible in Picture, Misuc, or other built-in apps, you will have to use Media Scanner. To make this happend, use scanFile method in fs.

RNFetchBlog
    .config({
        // DCIMDir is in external storage
        path : dirs.DCIMDir + '/music.mp3'
    })
    .fetch('GET', 'http://example.com/music.mp3')
    .then((res) => RNFetchBlob.fs.scanFile([ { path : res.path(), mime : 'audio/mpeg' } ]))
    .then(() => {
        // scan file success
    })
    .catch((err) => {
        // scan file error
    })

If mime is null or undefined, then the mime type will be inferred from the file extension.

Download Notification and Visibiliy in Download App (Android Only)

If you want to display a notification when file’s completely download to storage (as the above), or make the downloaded file visible in “Downloads” app. You have to add some options to config.

RNFetchBlob.config({
  fileCache : true,
  // android only options, these options be a no-op on IOS
  addAndroidDownloads : {
    // Show notification when response data transmitted
    notification : true,
    // Title of download notification
    title : 'Great ! Download Success ! :O ',
    // File description (not notification description)
    description : 'An image file.',
    mime : 'image/png',
    // Make the file scannable  by media scanner
    meidaScannable : true,
  }
})
.fetch('GET', 'http://example.com/image1.png')
.then(...)

File Access

File access APIs were made when developing v0.5.0, which helping us write tests, and was not planned to be a part of this module. However I realized that, it’s hard to find a great solution to manage cached files, every one who use this moudle may need those APIs for there cases.

Here’s the list of fs APIs

• dirs
• createFile
• readStream
• writeStream
• unlink
• mkdir
• ls
• mv
• cp
• exists
• isDir
• lstat
• stat
• scanFile (Android Only)

See fs chapter for more information

File Stream

In v0.5.0 we’ve added writeStream and readStream, which allows your app read/write data from file path. This API creates a file stream, rather than convert whole data into BASE64 encoded string, it’s handy when processing large files.

When calling readStream method, you have to open the stream, and start to read data.

let data = ''
RNFetchBlob.readStream(
    // encoding, should be one of `base64`, `utf8`, `ascii`
    'base64',
    // file path
    PATH_TO_THE_FILE,
    // (optional) buffer size, default to 4096 (4095 for BASE64 encoded data)
    // when reading file in BASE64 encoding, buffer size must be multiples of 3.
    4095)
.then((ifstream) => {
    ifstream.open()
    ifstream.onData((chunk) => {
      // when encoding is `ascii`, chunk will be an array contains numbers
      // otherwise it will be a string
      data += chunk
    })
    ifstream.onError((err) => {
      console.log('oops', err)
    })
    ifstream.onEnd(() => {  
      <Image source={{ uri : 'data:image/png,base64' + data }}
    })
})

When use writeStream, the stream is also opened immediately, but you have to write, and close by yourself.

RNFetchBlob.writeStream(
    PATH_TO_FILE,
    // encoding, should be one of `base64`, `utf8`, `ascii`
    'utf8',
    // should data append to existing content ?
    true)
.then((ofstream) => {
    ofstream.write('foo')
    ofstream.write('bar')
    ofstream.close()
})

Cache File Management

When using fileCache or path options along with fetch API, response data will automatically stored into file system. The files will NOT removed unless you unlink it. There’re several ways to remove the files

  // remove file using RNFetchblobResponse.flush() object method
  RNFetchblob.config({
      fileCache : true
    })
    .fetch('GET', 'http://example.com/download/file')
    .then((res) => {
      // remove cached file from storage
      res.flush()
    })

  // remove file by specifying a path
  RNFetchBlob.fs.unlink('some-file-path').then(() => {
    // ...
  })

You can also grouping requests by using session API, and use dispose to remove them all when needed.

  RNFetchblob.config({
    fileCache : true
  })
  .fetch('GET', 'http://example.com/download/file')
  .then((res) => {
    // set session of a response
    res.session('foo')
  })  

  RNFetchblob.config({
    // you can also set session beforehand
    session : 'foo'
    fileCache : true
  })
  .fetch('GET', 'http://example.com/download/file')
  .then((res) => {
    // ...
  })  

  // or put an existing file path to the session
  RNFetchBlob.session('foo').add('some-file-path')
  // remove a file path from the session
  RNFetchBlob.session('foo').remove('some-file-path')
  // list paths of a session
  RNFetchBlob.session('foo').list()
  // remove all files in a session
  RNFetchBlob.session('foo').dispose().then(() => { ... })

---

API

config(options:RNFetchBlobConfig):fetch

0.5.0

Config API was introduced in v0.5.0 which provides some options for the fetch task.

see RNFetchBlobConfig

fetch(method, url, headers, body):Promise<FetchBlobResponse>

legacy

Send a HTTP request uses given headers and body, and return a Promise.

method:string Required

HTTP request method, can be one of get, post, delete, and put, case-insensitive.

url:string Required

HTTP request destination url.

headers:object (Optional)

Headers of HTTP request, value of headers should be stringified, if you’re uploading binary files, content-type should be application/octet-stream or multipart/form-data(see examples above).

body:string | Array<Object> (Optional)

Body of the HTTP request, body can either be a BASE64 string, or an array contains object elements, each element have 2 required property name, and data, and 1 optional property filename, once filename is set, content in data property will be consider as BASE64 string that will be converted into byte array later. When body is a base64 string , this string will be converted into byte array in native code, and the request body will be sent as application/octet-stream.

fetch(...).progress(eventListener):Promise<FetchBlobResponse>

0.4.2

Register on progress event handler for a fetch request.

eventListener:(sendOrReceivedBytes:number, totalBytes:number)

A function that triggers when there’s data received/sent, first argument is the number of sent/received bytes, and second argument is expected total bytes number.

wrap(path:string):string

Simply prepend RNFetchBlob-file:// to a path, this make the file path becomes recognizable to native fetch method.

session(name:string):RNFetchBlobSession

Session API helps managing cached files, the following code, will try to return an existing session object with the given name, if it does not exist, create one.

RNFetchBlob.session('mysession')

see Class RNFetchBlobSession for usage.

base64

0.4.2

A helper class simply uses base-64 for decode and encode BASE64 data.

RNFetchBlob.base64.encode(data)
RNFetchBlob.base64.decode(data)

fs

0.5.0

dirs

This constant is a hash map contains common used folders:

• DocumentDir
• CacheDir
• DCIMDir (Android Only)
• DownloadDir (Android Only)
• MusicDir (Android Only)
• PictureDir (Android Only)
• MovieDir (Android Only)
• RingtoneDir (Android Only)

const dirs = RNFetchBlob.fs.dirs
console.log(dirs.DocumentDir)
console.log(dirs.CacheDir)
console.log(dirs.DCIMDir)
console.log(dirs.DownloadDir)

If you’re going to make downloaded file visible in Android Downloads app, please see Show Downloaded File and Notification in Android Downloads App.

createFile(path, data, encoding):Promise

path:string

The path which this new file will be created.

data:string | Array<number>

Content of the new file, when encoding is ascii, this argument shoud be an array contains number 0~255.

encoding:utf8 | base64 | ascii

Encoding of content.

the following expressions are equivalent.

const fs = RNFetchBlob.fs
const base64 = RNFetchBlob.base64
fs.createFile(NEW_FILE_PATH, 'foo', 'utf8')
fs.createFile(NEW_FILE_PATH, [102, 111, 111], 'ascii')
fs.createFile(NEW_FILE_PATH, base64.encode('foo'), 'base64')

writeStream(path:string, encoding:string, append:boolean):Promise

path:string

The path to the file the stream is writing to.

encoding:utf8 | base64 | ascii

Encoding of input data.

append:boolean(optional, default to false)

Will new data append after existing file or not.

Calling writeStream method will returns a Promise, which resolves a RNFetchBlobWriteSteam instance when stream opened successfully.

// write utf8 data
RNFetchBlob.fs.writeStream(PATH_TO_WRITE, 'utf8')
    .then((stream) => {
        stream.write('foo')
        return stream.close()
    })
// write ASCII data
RNFetchBlob.fs.writeStream(PATH_TO_WRITE, 'ascii')
    .then((stream) => {
        // write char `f`
        stream.write([102])
        // write char `o`, `o`
        stream.write([111,111])
        return stream.close()
    })
// write BASE64
RNFetchBlob.fs.writeStream(PATH_TO_WRITE, 'base64')
    .then((stream) => {
        stream.write(RNFetchBlob.base64.encode('foo'))
        return stream.close()
    })

readStream(path, encoding, bufferSize):Promise

path:string

The path to the file the stream is reading from.

encoding:string

Encoding of the data.

bufferSize:number(optional)

Buffer size of read stream, default to 4096 and 4095(when encoding is base64)

readStream returns a promise which will resolve RNFetchBlobReadStream.

RNFetchBlob.fs.readStream(PATH_TO_READ, 'utf8')
    .then((stream) => {
        let data = ''
        stream.open()
        stream.onData((chunk) => {
            chunk += data
        })
        stream.onEnd(() => {
            console.log(data)
        })
    })

mkdir(path:string):Promise

Create a directory named path

RNFetchBlob.fs.mkdir(PATH_TO_CREATE)
.then(() => { ... })
.catch((err) => { ... })

ls(path:string):Promise>

List files and directories in a path

RNFetchBlob.fs.ls(PATH_TO_LIST)
    // files will an array contains filenames
    .then((files) => {
        console.log(files)
    })

mv(from:string, to:string):Promise

Move a file’s location

RNFetchBlob.fs.mv(FROM_PATH, TO_PATH)
.then(() => { ... })
.catch(() => { ... })

cp(src:string, dest:string):Promise

Copy a file.

RNFetchBlob.fs.mv(SRC_PATH, DEST_PATH)
.then(() => { ... })
.catch(() => { ... })

exists(path:string):Promise

Check if a file exist at path

RNFetchBlob.fs.exists(PATH_OF_FILE)
.then((exist) => {
    console.log(`file ${exist ? '' : 'not'} exists`)
})
.catch(() => { ... })

isDir(path:string):Promise

Check the file at path is a directory or not. Resolves with false when the path is not a directory, or it does not exists.

RNFetchBlob.fs.exists(PATH_OF_FILE)
.then((isDir) => {
    console.log(`file is ${isDir ? '' : 'not'} a directory`)
})

unlink(path:string):Promise

Delete a file at path

RNFetchBlob.fs.unlink(path)
.then(() => { ... })
.catch((err) => { ... })

lstat(path:string):Promise

Get statistic data of files in a directory, the result data will be an array of RNFetchBlobStat.

RNFetchBlob.fs.lstat(PATH_OF_A_FOLDER)
    .then((stats) => {})
    .catch((err) => {})

stat(path:string):Promise

Similar get statistic a data or a directory. the result data will be a RNFetchBlobStat.

RNFetchBlob.fs.stat(PATH_OF_THE_TARGET)
    .then((stats) => {})
    .catch((err) => {})

scanFile(path:string):Promise (Androi Only)

Connect Media Scanner and scan the file. see Android Media Scanner, and Downloads App Support chapter for more information.

---

Types

RNFetchBlobConfig

A set of configurations that will be injected into a fetch method, with the following properties.

fileCache:boolean

Set this property to true will makes response data of the fetch stored in a temp file, by default the temp file will stored in App’s own root folder with file name template RNFetchBlob_tmp${timestamp}.

appendExt:string

Set this propery to change temp file extension that created by fetch response data.

path:string

When this property has value, fetch API will try to store response data in the path ignoring fileCache and appendExt property.

addAndroidDownloads:object (Android only)

This is an Android only property, it should be an object with the following properties :

• title : title of the file
• description : File description of the file.
• mime : MIME type of the file. By default is text/plain
• mediaScannable : A boolean value, see Officail Document
• notification : A boolean value decide whether show a notification when download complete.

RNFetchBlobResponse

When fetch success, it resolve a FetchBlobResponse object as first argument. FetchBlobResponse object has the following methods (these method are synchronous, so you might take quite a performance impact if the file is big)

base64():string

returns base64 string of response data (done in native context)

json():object

returns json parsed object (done in js context)

text():string

returns decoded base64 string (done in js context)

path():string

returns file path if the response data is cached in file

session(name:string):RNFetchBlobSession

when the response data is cached in a file, this method adds the file into the session. The following usages are equivalent.

RNFetchBlob.session('session-name').add(resp.path())
// or
resp.session('session-name')

RNFetchBlobStat

Statistic data of a file, see the following sample object.

{
    // file name
    filename : 'foo.png',
    // folder of the file or the folder itself
    path : '/path/to/the/file/wihout/file/name/',
    // size in byte
    size : 4901,
    // `file` or `directory`
    type : 'file',
    // last modified timestamp
    lastModified : 141323298
}

RNFetchBlobSession

A session is an object that helps you manage files. It simply main a list of file path and let you use dispose()to delete files in this session once and for all.

add(path:string):RNFetchBlobSession

Add a file path to this session.

remove(path:string):RNFetchBlobSession

Remove a file path from this session (not delete the file).

list():Array

Returns an array contains file paths in this session.

dispose():Promise

Delete all files according to paths in the session.

Major Changes

Version
0.5.2	Fix improper url params bug #26 and change IOS HTTP implementation from NSURLConnection to NSURLSession
0.5.0	Upload/download with direct access to file storage, and also added file access APIs
0.4.2	Supports upload/download progress
0.4.1	Fixe upload form-data missing file extension problem on Android
0.4.0	Add base-64 encode/decode library and API
~0.3.0	Upload/Download octet-stream and form-data

TODO

• Customizable Multipart MIME type

In Progress (v0.6.0)

• Add readFile and WriteFile API to fs
• Add file access API for direct access RNFetchBlobResponse when the response is a file path
• Android Download Manager file download API

Development

If you’re interested in hacking this module, check our development guide, there might be some helpful information. Please feel free to make a PR or file an issue.