Summary:
Adds support for JS async methods and helps guide people writing native modules w.r.t. the callbacks. With this diff, on the native side you write:
```objc
RCT_EXPORT_METHOD(getValueAsync:(NSString *)key
resolver:(RCTPromiseResolver)resolve
rejecter:(RCTPromiseRejecter)reject)
{
NSError *error = nil;
id value = [_nativeDataStore valueForKey:key error:&error];
// "resolve" and "reject" are automatically defined blocks that take
// any object (nil is OK) and an NSError, respectively
if (!error) {
resolve(value);
} else {
reject(error);
}
}
```
On the JS side, you can write:
```js
var {DemoDataStore} = require('react-native').NativeModules;
DemoDataStore.getValueAsync('sample-key').then((value) => {
console.log('Got:', value);
}, (error) => {
console.error(error);
// "error" is an Error object whose message is the NSError's description.
// The NSError's code and domain are also set, and the native trace i
Closes https://github.com/facebook/react-native/pull/1232
Github Author: James Ide <ide@jameside.com>
Test Plan: Imported from GitHub, without a `Test Plan:` line.
James Ide
Spencer Ahrens
Tadeu Zagallo
Andy Street
Kevin Gozali
Marshall Roch
Christopher Chedeau