Use PostCSS to style your React Native apps.
Behind the scenes the PostCSS files are transformed to react native style objects (look at the examples).
This transformer can be used together with React Native CSS modules.
Your App.css
file might look like this (using postcss-css-variables plugin):
:root {
--blue-color: blue;
}
.myClass {
color: var(--blue-color);
}
.myOtherClass {
color: red;
}
.my-dashed-class {
color: green;
}
When you import your stylesheet:
import styles from "./App.css";
Your imported styles will look like this:
var styles = {
myClass: {
color: "blue"
},
myOtherClass: {
color: "red"
},
"my-dashed-class": {
color: "green"
}
};
You can then use that style object with an element:
Plain React Native:
<MyElement style={styles.myClass} />
<MyElement style={styles["my-dashed-class"]} />
React Native CSS modules using className property:
<MyElement className={styles.myClass} />
<MyElement className={styles["my-dashed-class"]} />
React Native CSS modules using styleName property:
<MyElement styleName="myClass my-dashed-class" />
yarn add --dev react-native-postcss-transformer postcss
Add your PostCSS configuration to one of the supported config formats, e.g. package.json
, .postcssrc
, postcss.config.js
, etc.
Add this to metro.config.js
in your project's root (create the file if it does not exist already):
const { getDefaultConfig } = require("metro-config");
module.exports = (async () => {
const {
resolver: { sourceExts }
} = await getDefaultConfig();
return {
transformer: {
babelTransformerPath: require.resolve("./postcss-transformer.js")
},
resolver: {
sourceExts: [...sourceExts, "css", "pcss"]
}
};
})();
If you are using Expo, you also need to add this to app.json
:
{
"expo": {
"packagerOpts": {
"config": "metro.config.js"
}
}
}
If you are using React Native without Expo, add this to rn-cli.config.js
in your project's root (create the file if you don't have one already):
module.exports = {
getTransformModulePath() {
return require.resolve("./postcss-transformer.js");
},
getSourceExts() {
return ["js", "jsx", "css", "pcss"]; // <-- Add other extensions if needed.
}
};
If you are using Expo, instead of adding the rn-cli.config.js
file, you need to add this to app.json
:
{
"expo": {
"packagerOpts": {
"sourceExts": ["js", "jsx", "css", "pcss"],
"transformer": "./postcss-transformer.js"
}
}
}
Create postcss-transformer.js
file to your project's root and specify supported extensions:
// For React Native version 0.59 or later
var upstreamTransformer = require("metro-react-native-babel-transformer");
// For React Native version 0.56-0.58
// var upstreamTransformer = require("metro/src/reactNativeTransformer");
// For React Native version 0.52-0.55
// var upstreamTransformer = require("metro/src/transformer");
// For React Native version 0.47-0.51
// var upstreamTransformer = require("metro-bundler/src/transformer");
// For React Native version 0.46
// var upstreamTransformer = require("metro-bundler/build/transformer");
var postcssTransformer = require("react-native-postcss-transformer");
var postCSSExtensions = ["css", "pcss"]; // <-- Add other extensions if needed.
module.exports.transform = function({ src, filename, options }) {
if (postCSSExtensions.some(ext => filename.endsWith("." + ext))) {
return postcssTransformer.transform({ src, filename, options });
}
return upstreamTransformer.transform({ src, filename, options });
};
This library has the following Node.js modules as dependencies:
- Find a way to make the configuration cleaner by only having to add
metro.config.js
to a project, kristerkari#1.