just_audio/ios/Classes/JustAudioPlugin.m

#import "JustAudioPlugin.h"
#import "AudioPlayer.h"
#import "AudioPlayer.h"

@implementation JustAudioPlugin {
  NSObject<FlutterPluginRegistrar>* _registrar;
}

+ (void)registerWithRegistrar:(NSObject<FlutterPluginRegistrar>*)registrar {
  FlutterMethodChannel* channel = [FlutterMethodChannel
    methodChannelWithName:@"com.ryanheise.just_audio.methods"
          binaryMessenger:[registrar messenger]];
  JustAudioPlugin* instance = [[JustAudioPlugin alloc] initWithRegistrar:registrar];
  [registrar addMethodCallDelegate:instance channel:channel];
}

- (instancetype)initWithRegistrar:(NSObject<FlutterPluginRegistrar> *)registrar {
  self = [super init];
  NSAssert(self, @"super init cannot be nil");
  _registrar = registrar;
  return self;
}

- (void)handleMethodCall:(FlutterMethodCall*)call result:(FlutterResult)result {
  if ([@"init" isEqualToString:call.method]) {
    NSString* playerId = call.arguments;
    AudioPlayer* player = [[AudioPlayer alloc] initWithRegistrar:_registrar playerId:playerId];
    result(nil);
  } else {
    result(FlutterMethodNotImplemented);
  }
}

@end