Trying to put a global NSMutable Array in Objective C - objective-c

Question

I`m making an exercise, i have 2 classes Songs and Playlist, in the program i can put songs in playlist and everything is working fine, but i need to make a master playlist with all the songs that are in all the normal playlist and there is the problem.
Here is the code
//
// main.m
// MyItunes
//
// Created by Rodrigo López on 6/29/12.
// Copyright (c) 2012 ITQ. All rights reserved.
//
#import <Foundation/Foundation.h>
#import "Songs.h"
#import "PlayList.h"
int main (int argc, const char * argv[])
{
#autoreleasepool {
Songs *mySong1 = [Songs new];
Songs *mySong2 = [Songs new];
Songs *mySong3 = [Songs new];
PlayList *myPlayList1=[[PlayList alloc]initWithName:#"First"];
PlayList *myPlayList2=[[PlayList alloc]initWithName:#"Second"];
[mySong1 setTitle:#"Back In Black" setArtist:#"AC/DC" setAlbum:#"Back In Black" setPlayt:#"4:16"];
[mySong2 setTitle:#"Medicate" setArtist:#"AFI" setAlbum:#"Crash Love" setPlayt:#"4:21"];
[mySong3 setTitle:#"Rucci" setArtist:#"Austin TV" setAlbum:#"La ultima noche" setPlayt:#"4:39"];
[myPlayList1 addSong:mySong1];
[myPlayList1 addSong:mySong2];
[myPlayList2 addSong:mySong3];
[myPlayList1 showPlayList];
[myPlayList2 showPlayList];
[myPlayList1 showPlayList];
[myPlayList1 showAllSongs];
}
return 0;
}
//
// PlayList.m
// MyItunes
//
// Created by Rodrigo López on 6/29/12.
// Copyright (c) 2012 ITQ. All rights reserved.
//
#import "PlayList.h"
#implementation PlayList
#synthesize playListarray,playListName;
-(id) initWithName: (NSString *) name
{
if(self)
{
playListName = [NSString stringWithString: name];
playListarray = [NSMutableArray array];
playlistMaster=[NSMutableArray array ];
}
return self;
}
-(void) addSong: (Songs *) theSong
{
[playListarray addObject:theSong];
[playlistMaster addObject:theSong];
}
-(void) showPlayList
{
NSLog(#"Play List: %#", self.playListName);
for(Songs *theSong in playListarray)
{
NSLog(#"%#", theSong.title);
}
}
-(void) showAllSongs
{
NSLog(#"Play List: Master");
for(Songs *theSong in playlistMaster)
{
NSLog(#"%#", theSong.title);
}
}
-(NSUInteger) entries
{
return [playListarray count];
}
-(void) remove: (Songs *) theSong
{
[playListarray removeObjectIdenticalTo:theSong];
}
#end
The problem is with the NSMutable array, i want to declare the array globally, but i dont know how to do it, here is the output of this program:
2012-06-29 19:24:06.061 MyItunes[17184:707] Play List: First
2012-06-29 19:24:06.080 MyItunes[17184:707] Back In Black
2012-06-29 19:24:06.083 MyItunes[17184:707] Medicate
2012-06-29 19:24:06.084 MyItunes[17184:707] Play List: Second
2012-06-29 19:24:06.085 MyItunes[17184:707] Rucci
2012-06-29 19:24:06.089 MyItunes[17184:707] Play List: First
2012-06-29 19:24:06.090 MyItunes[17184:707] Back In Black
2012-06-29 19:24:06.091 MyItunes[17184:707] Medicate
2012-06-29 19:24:06.091 MyItunes[17184:707] Play List: Master
2012-06-29 19:24:06.092 MyItunes[17184:707] Back In Black
2012-06-29 19:24:06.093 MyItunes[17184:707] Medicate
So in play list master, its missing Rucci song, hope you can help me, thank you very much, i appreciate it

Answer 1

I would make your playlistMaster a "static variable" of the PlayList implementation file as described at: Objective C Static Class Level variables. You just declare and initialize it the .m file outside of any other methods. (Don't forget to make sure it is retained.)
I should also note that there are some memory issues in your PlayList class. In particular, your initializer code should retain the member variables, like:
-(id) initWithName: (NSString *) name
{
if (self = [super init]) {
playListName = [[NSString stringWithString: name] retain]; // NOTE: You could also do: [[NSString alloc] initWithString: name];
playListarray = [[NSMutableArray array] retain]; // NOTE: You could also do: [[NSMutableArray alloc] init];
playlistMaster = [[NSMutableArray array] retain]; // ditto
}
return self;
}
If you do this, you will need to add a dealloc method that releases each of these. But if you don't they may be released before you try to use them.