Question

我正在练习，我有两个类歌曲和播放列表，在程序中我可以将歌曲放在播放列表中，一切正常，但我需要制作一个主播放列表，其中包含所有歌曲正常的播放列表，有问题。

这是代码

    //
//  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

问题在于NSMutable数组，我想全局声明数组，但我不知道怎么做，这是这个程序的输出：

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

所以在播放列表大师，它失踪的Rucci歌曲，希望你能帮助我，非常感谢你，我很感激

Answer 1

我会将您的播放列表主播设为播放列表实现文件的“静态变量”，如下所述：Objective C Static Class Level variables。您只需在任何其他方法之外声明并初始化.m文件。（不要忘记确保它被保留。）

我还应该注意PlayList类中存在一些内存问题。特别是，初始化代码应保留成员变量，如：

-(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;
}

如果您这样做，则需要添加dealloc方法来释放其中的每一个。但如果你不这样做，他们可能会在你尝试使用之前被释放。

试图在Objective C中放置一个全局的NSMutableArray

1 个答案: