Adding an object to Mutable array is not possible - objective-c

Question

I am trying add a Song* object to a Mutable array and I am stumped as the count of the array is not increasing in spite of adding the object.
Song.h
#import <Foundation/Foundation.h>
#interface Song : NSObject
#property(copy, nonatomic) NSString *title, *album, *artist;
#property(copy, nonatomic) NSNumber *playTime;
#end
Song.m
#import "Song.h"
#implementation Song
#end
Playlist.h
#import <Foundation/Foundation.h>
#class Song;
#interface Playlist : NSObject
#property(copy, nonatomic) NSMutableArray *playListArray;
-(void) addSong: (Song *) tempSongToBeAdded;
-(void) removeSong: (Song *) tempSongToBeremoved;
-(void) listOfSongs;
-(NSUInteger) entries;
#end
Playlist.m
#import "Playlist.h"
#import "Song.h"
#implementation Playlist
-(void) addSong: (Song *) tempSongToBeAdded{
NSLog(#"%s song is being added.", [tempSongToBeAdded.title UTF8String]);
[self.playListArray addObject:tempSongToBeAdded];
}
-(void) removeSong: (Song *) tempSongToBeremoved{
[self.playListArray removeObject:tempSongToBeremoved];
}
-(NSUInteger) entries{
return [self.playListArray count];
}
-(void) listOfSongs{
NSLog(#"Hi");
for (Song *tempSong in self.playListArray) {
NSLog(#"title: %s", [tempSong.title UTF8String]);
}
}
#end
Main.m
#import <Foundation/Foundation.h>
#import "Song.h"
#import "Playlist.h"
int main(int argc, const char * argv[])
{
#autoreleasepool {
Song *song1 = [[Song alloc] init];
song1.title = #"Manasa";
song1.album = #"Ye Maya Chesava";
song1.artist = #"A. R. Rahman";
song1.playTime = [NSNumber numberWithDouble:4.56];
Playlist *playlist1 = [[Playlist alloc] init];
[playlist1 addSong:song1];
NSLog(#"The total number of songs are %lu",[playlist1 entries]);
[playlist1 listOfSongs];
}
return 0;
}
I am getting the entries in the playlist as 0 and and the list of songs as empty. I am not getting any compile errors and I have no idea why the objects are not getting added to the array.

Answer 1

Your variable playListArray is never initialized and is always nil. You need to initialize it using:
playListArray = [[NSMutableArray] alloc] init];
You can add an init method in your Playlist class where you initialize this object.
- (id)init
{
self = [super init];
if (self)
{
playListArray = [[NSMutableArray] alloc] init];
}
return self;
}
EDIT:
The problem seems to be how you declared the property
#property(copy, nonatomic) NSMutableArray *playListArray;
It is declared as copy, that means that even when you do playListArray = [[NSMutableArray] alloc] init], your variable playListArray gets a copy of the initialized array, but the copy protocol is inherited from NSArray, not from NSMutableArray, so you get an immutable array. You can check this in the NSMutableArray documentation. You need to change copy for retain (you're not using ARC, right?).
In fact I see that you're using copy for most of your properties, if there's no particular reason for this, I would change them to retain.