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Platform isAndroid, isIOS, and isNative properties
Ryan Linton
2023-06-14

RFC0670: Platform isAndroid, isIOS, and isNative properties

Summary

Add isAndroid, isIOS, and isNative to Platform.

Basic example

if (Platform.isAndroid) {
  // do some Android only stuff here
}

Motivation

Platform already defines isPad, isTV, and isTesting. In consulting and the companies I've worked at I've seen dozens (even hundreds) of apps, and nearly all backfill the missing ones isAndroid and isIOS with something along the lines of the following:

const isAndroid = Platform.OS === "android";
const isIOS = Platform.OS === "ios";

Platform should provide these since so many devs want to express one-off platform checks this way.

Detailed design

I did an initial implementation here but it has some drawbacks. As @NickGerleman pointed out we don't want to maintain a centralized list of platforms. A better solution that keeps the platform definitions in their respective platforms is to update Platform to be a proxy object.

const Platform = new Proxy(
  {
    __constants: null,
    OS: "android",
    isAndroid: true,
    isNative: true,
    // ...
  },
  {
    get(target, prop) {
      if (prop in target) {
        return target[prop];
      }

      if (prop.toString().startsWith("is")) {
        return false;
      }

      return Reflect.get(...arguments);
    },
  }
);

Drawbacks

  • This change doesn't really offer any new functionality over conditional logic using Platform.OS. It's just a different (albeit quite common) way of expressing the same thing.
  • As @motiz88 points out this breaks existing optimizations with Babel transforms that remove dead code based on Platform.OS conditionals. This proposal likely further complicates that by making Platform a proxy object.
  • All other platforms would need to update their Platform implementations to match.

Alternatives

Another potential solution that doesn't use proxy but reads similarly would be to add an is method (e.g. Platform.is('android') or Platform.is('ios')). This may or may not have advantages considering the Babel transforms. It is less similar to the common code that inspired this proposal though.

Adoption strategy

This is not a breaking change but would be a new API offering the same existing functionality provided by checking against Platform.OS. Existing React Native developers would upgrade to latest and discover via docs and types.

How we teach this

Per motivation, React Native developers are already doing this. This just moves the definition of isAndroid and isIOS up into React Native.

Unresolved questions

  • Where are the Babel transforms for removing platform specific code and how do they work?