feat: expo config plugin for iOS native code

[castdrian]

it’d be cool if this lib would provide an expo config plugin to perform the native code change in the AppDelegate, since managed projects regenerate the native code when they build

[kesha-antonov]

Hi Nice idea! If you can please submit PR I can also check how to do it on the weekend

[castdrian]

Yeah I'll see to get to it if I have time, it's fairly easy to do thankfully, expo exposes direct apis to inject code into the AppDelegate, this is a nice explanation: https://www.sitepen.com/blog/doing-more-with-expo-using-custom-native-code

[kesha-antonov]

Thanks for the hint!

[mtshv]

Yo guys, Sharing my expo config plugin for AppDelegate modification. Works fine so far:

const { withAppDelegate } = require('@expo/config-plugins');

function withRNBackgroundDownloader(expoConfig) {
  return withAppDelegate(expoConfig, async appDelegateConfig => {
    const { modResults: appDelegate } = appDelegateConfig;
    const appDelegateLines = appDelegate.contents.split('\n');

    // Define the code to be added to AppDelegate.mm
    const backgroundDownloaderImport =
      '#import <RNBackgroundDownloader.h> // Required by react-native-background-downloader. Generated by expoPlugins/withRNBackgroundDownloader.js';
    const backgroundDownloaderDelegate = `\n// Delegate method required by react-native-background-downloader. Generated by expoPlugins/withRNBackgroundDownloader.js
- (void)application:(UIApplication *)application handleEventsForBackgroundURLSession:(NSString *)identifier completionHandler:(void (^)(void))completionHandler
{
  [RNBackgroundDownloader setCompletionHandlerWithIdentifier:identifier completionHandler:completionHandler];
}`;

    // Find the index of the AppDelegate import statement
    const importIndex = appDelegateLines.findIndex(line =>
      /^#import "AppDelegate.h"/.test(line),
    );

    // Find the index of the last line before the @end statement
    const endStatementIndex = appDelegateLines.findIndex(line =>
      /@end/.test(line),
    );

    // Insert the import statement if it's not already present
    if (!appDelegate.contents.includes(backgroundDownloaderImport)) {
      appDelegateLines.splice(importIndex + 1, 0, backgroundDownloaderImport);
    }

    // Insert the delegate method above the @end statement
    if (!appDelegate.contents.includes(backgroundDownloaderDelegate)) {
      appDelegateLines.splice(
        endStatementIndex,
        0,
        backgroundDownloaderDelegate,
      );
    }

    // Update the contents of the AppDelegate file
    appDelegate.contents = appDelegateLines.join('\n');

    return appDelegateConfig;
  });
}

module.exports = withRNBackgroundDownloader;

I'd open a PR to add it, but I do not know the appropriate place to put this code 🤷

[castdrian]

yup that config plugin works like a charm, well done