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POSending a message to an object
 

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    <p>I'm pretty new to Objective C but things are progressing well. However, I think I'm missing a key concept relating to how objects are created and messaged. I hope someone can help me.</p> <p>I'm creating an iPhone app that simply creates a MPMusicPlayer, and starts playing a song from the que.</p> <p>I create the music player (myPlayer) in the AppDelegate like so...</p> <pre><code>- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { // Override point for customization after application launch. // Add the main view controller's view to the window and display. [window addSubview:mainViewController.view]; [window makeKeyAndVisible]; // instantiate a music player MPMusicPlayerController *myPlayer = [MPMusicPlayerController applicationMusicPlayer]; // assign a playback queue containing all media items on the device [myPlayer setQueueWithQuery: [MPMediaQuery songsQuery]]; // start playing from the beginning of the queue [myPlayer play]; return YES; </code></pre> <p>}</p> <p>This works fine. Now in the MainViewController I try to send myPlayer the command to skip to the next track </p> <pre><code>[myPlayer skipToNextItem]; </code></pre> <p>However when I try to compile I get the message that myPlayer in undeclared.</p> <p>What am I doing wrong? I can see how I could fix this in a procedural way (by creating the player in the MainViewController), but I'd like to understand what I have to do to get it working in and OOP way.</p> <p>Cheers,</p> <p>Richard</p>
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