React Native: require() with Dynamic String?

Question

I have read several posts about issues that people are having with React Native and the require() function when trying to require a dynamic resource such as:

Dynamic (fails):

urlName = "sampleData.json";
data = require('../' + urlName);

vs. Static (succeeds):

data = require('../sampleData.json');

I have read on some threads that this is a bug in React Native and in others that this is a feature.

Is there a new way to require a dynamic resource within a function?

Related Posts (all fairly old in React time):

• Importing Text from local json file in React native
• React Native - Dynamically List/Require Files In Directory
• React Native - Image Require Module using Dynamic Names
• React Native: how to use require(path) with dynamic urls?

Answer 1

As i have heard of, react's require() only uses static url not variables, that means that you have to do require('/path/file'), take a look at this issue on github and this one for more alternative solutions, there are a couple of other ways to do it! for e.g

const images = {
profile: {
    profile: require('./profile/profile.png'),
    comments: require('./profile/comments.png'),
},
   image1: require('./image1.jpg'),
   image2: require('./image2.jpg'),
};

export default images;

then

import Images from './img/index';

render() {
    <Image source={Images.profile.comments} />
}

from this answer

Answer 2

Here is my solution.

Setup

File structure:

app  
  |--src
    |--assets
      |--images
        |--logos
          |--small_kl_logo.png
          |--small_a1_logo.png
          |--small_kc_logo.png
          |--small_nv_logo.png
          |--small_other_logo.png

        |--index.js
    |--SearchableList.js

In index.js, I have this:

const images = {
  logos: {
    kl: require('./logos/small_kl_logo.png'),
    a1: require('./logos/small_a1_logo.png'),
    kc: require('./logos/small_kc_logo.png'),
    nv: require('./logos/small_nv_logo.png'),
    other: require('./logos/small_other_logo.png'),
  }
};

export default images;

In my SearchableList.js component, I then imported the Images component like this:

import Images from './assets/images';

I then created a new function imageSelect in my component:

imageSelect = network => {
  if (network === null) {
    return Images.logos.other;
  }

  const networkArray = {
    'KL': Images.logos.kl,
    'A1': Images.logos.a1,
    'KC': Images.logos.kc,
    'NV': Images.logos.nv,
    'Other': Images.logos.other,
  };

  return networkArray[network];
};

Then in my components render function I call this new imageSelect function to dynamically assign the desired Image based on the value in the this.state.network:

render() {
  <Image source={this.imageSelect(this.state.network)} />
}

The value passed into the imageSelect function could be any dynamic string. I just chose to have it set in the state first and then passed in.

I hope this answer helps. :)

Answer 3

For anyone reading this that cannot work with the existing answers, I have an alternative.

First I'll explain my scenario. We have a mono repo with a number of packages (large react-native app). I want to dynamically import a bunch of locale files for i18n without having to keep a central registry in some magic file. There could be a number of teams working in the same monorepo and the DX we want is for package developers to be able to just add their local files in a known folder {{packageName}}/locales/en.json and have our core i18n functionality pick up their strings.

After several less than ideal solutions, I finally landed on https://github.com/kentcdodds/babel-plugin-preval as an ideal solution for us. This is how I did it:

const packageEnFiles = preval`
  const fs = require('fs');
  const path = require('path');

  const paths = [];

  const pathToPackages = path.join(__dirname, '../../../../packages/');
fs.readdirSync(pathToPackages)
    .filter(name => fs.lstatSync(path.join(pathToPackages, name)).isDirectory())
    .forEach(dir => {
      if (fs.readdirSync(path.join(pathToPackages, dir)).find(name => name === 'locales')) {
        const rawContents = fs.readFileSync(path.join(pathToPackages, dir, 'locales/en.json'), 'utf8');
        paths.push({
          name: dir,
          contents: JSON.parse(rawContents),
        });
      }
    });

  module.exports = paths;
`;

Then I can just iterate over this list and add the local files to i18next:

packageEnFiles.forEach(file => {
  i18n.addResourceBundle('en', file.name, file.contents);
});

Answer 4

Hey lads I rounded another way to require It's ugly but works. Images dynamically. Instead of storing your URL in the state you store the entire JSX. For an example:

state = {
  image: []
};

Instead of

let imageURL = `'../assets/myImage.png'`
this.state.image = imageURL

You use

let greatImage = (<Image source={require(../assets/myImage.png)}></Image>)
this.state.image = greatImage

To render in the JSX

{this.state.image}

You can style your image in the variable too. I had to use some if statements to render some images dynamically and after break my head for 2 hours this was the way that solved my problem. Like I said It's ugly and probably wrong.

Answer 5

If you need to switch between multiple locally stored images, you can also use this way:

        var titleImg;
        var textColor;
        switch (this.props.data.title) {
        case 'Футбол':
            titleImg = require('../res/soccer.png');
            textColor = '#76a963';
            break;
        case 'Баскетбол':
            titleImg = require('../res/basketball.png');
            textColor = '#d47b19';
            break;
        case 'Хоккей':
            titleImg = require('../res/hockey.png');
            textColor = '#3381d0';
            break;
        case 'Теннис':
            titleImg = require('../res/tennis.png');
            textColor = '#d6b031';
            break;
        }

In this snippet I change variables titleImg and textColor depending of the prop. I have put this snippet directly in render() method.

Answer 6

Simple to dynamic images (using require)

Example array(into state)

this.state={
       newimage: require('../../../src/assets/group/kids_room.png'),
       randomImages=[
         {
            image:require('../../../src/assets/group/kids_room.png')
          },
         {
            image:require('../../../src/assets/group/kids_room2.png')
          }
        ,
         {
            image:require('../../../src/assets/group/kids_room3.png')
          }
        
        
        ]

}

Trigger image( like when press button(i select image random number betwenn 0-2))

let setImage=>(){

this.setState({newimage:this.state.randomImages[Math.floor(Math.random() * 3)];
})
}

view

<Image
        style={{  width: 30, height: 30 ,zIndex: 500 }}
        
        source={this.state.newimage}
      />

Answer 7

I have found that a dynamic path for require() works when it starts with a static string. For example require("./" + path) works, whereas require(path) doesn't.

Answer 8

Are you using a module bundler like webpack?

If so, you can try require.ensure()

See: https://webpack.js.org/guides/code-splitting/#dynamic-imports

Answer 9

Reading through the docs, I've found a working answer and I'm able to use dynamic images, in the docs they refer to it as Network Images here

https://facebook.github.io/react-native/docs/images#network-images

Not sure if this can be applied to other file types, but as they list require with non image types

You would need to use the uri: call

data = {uri: urlName}

For me I got images working dynamically with this

<Image source={{uri: image}} />

Answer 10

Try the solution mentioned in this thread for Android. This solves the issue but unfortunately, it's only for android.

But make sure to run react-native run-android after every update. Else, the added images won't appear in the app.