Objective c 如何使用NSPredicate筛选包含来自其他类的复合对象的NSMutableSet？

新手问题

我有3个类，其中3个是NSOBject的子类

集合类，有两个属性，主歌曲作为NSMutableSet（强，非原子）和播放列表作为NSMUTABLEARY（强，非原子）

播放列表类

有两个属性，播放名为NSString（复制，非原子）和歌曲列表为NSMutableArray（强，非原子）

三,歌曲类

有4个属性：标题、艺术家、专辑、播放时间（复制、非原子）

---

masterSong将包含歌曲对象，listOfPlaylist将包含播放列表对象

而歌曲列表只存储对歌曲对象的引用

我想通过在masterSong中查找歌曲的标题、艺术家或专辑，为Collection类创建removeSong方法。

如果查找find 1，它将返回NSSet，返回的NSSet将作为参数出现在minusSet:方法中，以从masterSong和所有Playlist.songList中删除歌曲。

但是，我不知道如何写下NSPredicate语法，从包含Song对象的masterSong中筛选出.title或.album或.artist

这是我到目前为止所得到的 收藏

- (void) removeSong: (NSString *)zSong{

    //remove from reference playlist


    NSSet *targets = [self lookUpTitle:zSong];

    if ([targets count]>0) {
        [self.masterSongs minusSet:targets];

        for (Playlist *playlist in listOfPlaylists) {
            // -all objects converts the set into array.

            [playlist.songList removeObjectsInArray:[targets allObjects]];
        }
    }
    else
        ;
}

Xcode在执行lookUpTitle方法时抛出异常，表示由于未捕获的异常而终止应用程序“NSInvalidArgumentException”，原因：“无法查找字符串中的值（标题：整点不归，艺术家：Cafe Bleu，唱片集：CBSB，播放时间：3:56）（您知道什么）；值不是字符串

- (NSSet *) lookUpTitle: (NSString *)aName {

    NSString *filters = @"%K CONTAINS [cd] %@";
    NSPredicate *filter = [NSPredicate predicateWithFormat:filters, @"title", aName];

    NSSet *result = [masterSongs filteredSetUsingPredicate:filter];

    if ([result count] == 0) {
        NSLog(@"not found");

        return nil;
    }
    else{
        return result;
    }
}

我知道主要的问题是查找方法

 NSPredicate *filter = [NSPredicate predicateWithFormat:filters, @"title", aName];

 NSSet *result = [masterSongs filteredSetUsingPredicate:filter];

过滤器以错误的方式进行过滤，但它应该过滤NSString对象（标题、艺术家或唱片集），但masterSong包含歌曲对象，如何使用NSPredicate访问masterSong中放置的标题、艺术家、唱片集对象

对于这种情况，还有其他有效的方法吗

仅显示包含字符串的示例集/数组

我找到了另一个线程，但block读起来很混乱，在我的例子中仍然不起作用

---

编辑：根据响应者#1的请求添加部分代码（Class.m方法）。 下面是与我的问题相关的.m文件中的一些方法

Main.m

    #import <Foundation/Foundation.h>
#import "MusicCollection.h"
#import "Playlist.h"
#import "Song.h"
int main(int argc, const char * argv[])
{

    @autoreleasepool {

        // insert code here...
       // NSLog(@"Hello, World!");



        //create Songs

        Song *aSong = [[Song alloc]initWithTitle:@"Whole point of no return" withArtist:@"Cafe Bleu" withAlbum:@"CBSB" withPlaytime:@"3:56"];
        Song *bSong  = [[Song alloc]initWithTitle:@"Council Meetin'" withArtist:@"Cafe Bleu" withAlbum:@"CBSB" withPlaytime:@"4:00"];

        Song *cSong = [[Song alloc]initWithTitle:@"Hayate" withArtist:@"Spitz" withAlbum:@"Indigo Chiheisen" withPlaytime:@"4:21"];

        Song *dSong = [[Song alloc]initWithTitle:@"I have a Dreams" withArtist:@"WestLife" withAlbum:@"Season" withPlaytime:@"4:11"];

        Song *eSong = [[Song alloc]initWithTitle:@"What Do You Know" withArtist:@"David Choi" withAlbum:@"Tomorrow" withPlaytime:@"3:46"];


        //create playList

        Playlist *playlistA = [[Playlist alloc]initWithName:@"Playlist A"];

        Playlist *playListB = [[Playlist alloc]initWithName:@"Playlist B"];

    //store Song A & B to Playlist A and Song A,B,C to playlist B

        [playlistA addSong:aSong];

        [playlistA addSong:bSong];

        [playListB addSong:aSong];

        [playListB addSong:bSong];

        [playListB addSong:cSong];

//        [playListB removeSong:eSong];


//Creating Master Collection

        MusicCollection *myCollection = [[MusicCollection alloc]initWithName:@"Library"];

        [myCollection addPlaylist:playlistA];
        [myCollection addPlaylist:playListB];
        [myCollection addSong:eSong];
        [myCollection addSong:dSong];

        [myCollection removePlaylist:playListB];
        [myCollection removeSong:aSong];

        NSSet *container2 = [myCollection lookUpTitle:@"What"];

    NSLog(@"%@",container2);


    //    NSLog(@"%@",myCollection);
    }
    return 0;
}

-(instancetype) initWithName: (NSString *)aName{
    self = [super init];
    if (self) {

        self.name           = [NSMutableString stringWithString:aName];
        self.listOfPlaylists = [NSMutableArray array];
        self.masterSongs = [NSMutableSet set];


    }
    return self;
}

-(instancetype) init{

    return  [self initWithName:@""];

}

-(void) addPlaylist: (Playlist *)aPlayList{

    if ([listOfPlaylists containsObject:aPlayList]==YES) {

    }
    else
        [listOfPlaylists addObject:aPlayList];


}

-(void) removePlaylist: (Playlist *)aPlayList{
    if ([listOfPlaylists containsObject:aPlayList]) {

        [listOfPlaylists removeObjectIdenticalTo:aPlayList];
    }

    else{
        ;
    }

}

- (void) displaySong{

    NSLog(@"displaying all song in Collection");

    NSLog(@" %@",self.masterSongs);

}

- (void) addSong :(Song *)aSong{
    if (![masterSongs containsObject:aSong]) {

        [masterSongs addObject:aSong];

    }
}

- (void) removeSong: (NSString *)zSong{

    //remove from reference playlist


    NSSet *targets = [self lookUpTitle:zSong];

    if ([targets count]>0) {
        [self.masterSongs minusSet:targets];

        for (Playlist *playlist in listOfPlaylists) {
            // -all objects converts the set into array.

            [playlist.songList removeObjectsInArray:[targets allObjects]];
        }
    }
    else
        ;
}



 - (NSSet *) lookUpTitle: (NSString *)aName {

    NSString *filters = @"%K CONTAINS [cd] %@";
    NSPredicate *filter = [NSPredicate predicateWithFormat:filters, @"title", aName];

    NSSet *result = [masterSongs filteredSetUsingPredicate:filter];

    if ([result count] == 0) {
        NSLog(@"not found");

        return nil;
    }
    else{
        return result;
    }
}

- (void) addSong :(Song *)aSong{

    if (![songList containsObject:aSong]) {
        [songList addObject:aSong];
    }

}

- (void) removeSong: (Song *)aSong{
    if ([songList containsObject:aSong]){
    [self.songList removeObjectIdenticalTo:aSong];
    }
}
- (instancetype) initWithName: (NSString *)aPLName{
    self = [super init];

    if (self) {
        self.songList = [NSMutableArray array];
        self.playlistName = aPLName;
    }
    return self;
}

- (instancetype)init{
    return  [self initWithName:@""];
}

 - (instancetype) initWithTitle: (NSString *)aTitle withArtist: (NSString *)anArtist withAlbum: (NSString *)aAlbum withPlaytime: (NSString *)playingTime{

    self = [super init];

    if (self) {
        self.artist = [NSMutableString stringWithString:anArtist];
        self.album  = [NSMutableString stringWithString:aAlbum];
        self.title =   [NSMutableString stringWithString:aTitle];
        self.playtime = [NSMutableString stringWithString:playingTime];

    }
       return self;
}

-(instancetype) init{
    return  [self initWithTitle:@"null" withArtist:@"null" withAlbum:@"null" withPlaytime:@"null"];
}

Playlist.m

    #import <Foundation/Foundation.h>
#import "MusicCollection.h"
#import "Playlist.h"
#import "Song.h"
int main(int argc, const char * argv[])
{

    @autoreleasepool {

        // insert code here...
       // NSLog(@"Hello, World!");



        //create Songs

        Song *aSong = [[Song alloc]initWithTitle:@"Whole point of no return" withArtist:@"Cafe Bleu" withAlbum:@"CBSB" withPlaytime:@"3:56"];
        Song *bSong  = [[Song alloc]initWithTitle:@"Council Meetin'" withArtist:@"Cafe Bleu" withAlbum:@"CBSB" withPlaytime:@"4:00"];

        Song *cSong = [[Song alloc]initWithTitle:@"Hayate" withArtist:@"Spitz" withAlbum:@"Indigo Chiheisen" withPlaytime:@"4:21"];

        Song *dSong = [[Song alloc]initWithTitle:@"I have a Dreams" withArtist:@"WestLife" withAlbum:@"Season" withPlaytime:@"4:11"];

        Song *eSong = [[Song alloc]initWithTitle:@"What Do You Know" withArtist:@"David Choi" withAlbum:@"Tomorrow" withPlaytime:@"3:46"];


        //create playList

        Playlist *playlistA = [[Playlist alloc]initWithName:@"Playlist A"];

        Playlist *playListB = [[Playlist alloc]initWithName:@"Playlist B"];

    //store Song A & B to Playlist A and Song A,B,C to playlist B

        [playlistA addSong:aSong];

        [playlistA addSong:bSong];

        [playListB addSong:aSong];

        [playListB addSong:bSong];

        [playListB addSong:cSong];

//        [playListB removeSong:eSong];


//Creating Master Collection

        MusicCollection *myCollection = [[MusicCollection alloc]initWithName:@"Library"];

        [myCollection addPlaylist:playlistA];
        [myCollection addPlaylist:playListB];
        [myCollection addSong:eSong];
        [myCollection addSong:dSong];

        [myCollection removePlaylist:playListB];
        [myCollection removeSong:aSong];

        NSSet *container2 = [myCollection lookUpTitle:@"What"];

    NSLog(@"%@",container2);


    //    NSLog(@"%@",myCollection);
    }
    return 0;
}

-(instancetype) initWithName: (NSString *)aName{
    self = [super init];
    if (self) {

        self.name           = [NSMutableString stringWithString:aName];
        self.listOfPlaylists = [NSMutableArray array];
        self.masterSongs = [NSMutableSet set];


    }
    return self;
}

-(instancetype) init{

    return  [self initWithName:@""];

}

-(void) addPlaylist: (Playlist *)aPlayList{

    if ([listOfPlaylists containsObject:aPlayList]==YES) {

    }
    else
        [listOfPlaylists addObject:aPlayList];


}

-(void) removePlaylist: (Playlist *)aPlayList{
    if ([listOfPlaylists containsObject:aPlayList]) {

        [listOfPlaylists removeObjectIdenticalTo:aPlayList];
    }

    else{
        ;
    }

}

- (void) displaySong{

    NSLog(@"displaying all song in Collection");

    NSLog(@" %@",self.masterSongs);

}

- (void) addSong :(Song *)aSong{
    if (![masterSongs containsObject:aSong]) {

        [masterSongs addObject:aSong];

    }
}

- (void) removeSong: (NSString *)zSong{

    //remove from reference playlist


    NSSet *targets = [self lookUpTitle:zSong];

    if ([targets count]>0) {
        [self.masterSongs minusSet:targets];

        for (Playlist *playlist in listOfPlaylists) {
            // -all objects converts the set into array.

            [playlist.songList removeObjectsInArray:[targets allObjects]];
        }
    }
    else
        ;
}



 - (NSSet *) lookUpTitle: (NSString *)aName {

    NSString *filters = @"%K CONTAINS [cd] %@";
    NSPredicate *filter = [NSPredicate predicateWithFormat:filters, @"title", aName];

    NSSet *result = [masterSongs filteredSetUsingPredicate:filter];

    if ([result count] == 0) {
        NSLog(@"not found");

        return nil;
    }
    else{
        return result;
    }
}

- (void) addSong :(Song *)aSong{

    if (![songList containsObject:aSong]) {
        [songList addObject:aSong];
    }

}

- (void) removeSong: (Song *)aSong{
    if ([songList containsObject:aSong]){
    [self.songList removeObjectIdenticalTo:aSong];
    }
}
- (instancetype) initWithName: (NSString *)aPLName{
    self = [super init];

    if (self) {
        self.songList = [NSMutableArray array];
        self.playlistName = aPLName;
    }
    return self;
}

- (instancetype)init{
    return  [self initWithName:@""];
}

 - (instancetype) initWithTitle: (NSString *)aTitle withArtist: (NSString *)anArtist withAlbum: (NSString *)aAlbum withPlaytime: (NSString *)playingTime{

    self = [super init];

    if (self) {
        self.artist = [NSMutableString stringWithString:anArtist];
        self.album  = [NSMutableString stringWithString:aAlbum];
        self.title =   [NSMutableString stringWithString:aTitle];
        self.playtime = [NSMutableString stringWithString:playingTime];

    }
       return self;
}

-(instancetype) init{
    return  [self initWithTitle:@"null" withArtist:@"null" withAlbum:@"null" withPlaytime:@"null"];
}

Song.m

    #import <Foundation/Foundation.h>
#import "MusicCollection.h"
#import "Playlist.h"
#import "Song.h"
int main(int argc, const char * argv[])
{

    @autoreleasepool {

        // insert code here...
       // NSLog(@"Hello, World!");



        //create Songs

        Song *aSong = [[Song alloc]initWithTitle:@"Whole point of no return" withArtist:@"Cafe Bleu" withAlbum:@"CBSB" withPlaytime:@"3:56"];
        Song *bSong  = [[Song alloc]initWithTitle:@"Council Meetin'" withArtist:@"Cafe Bleu" withAlbum:@"CBSB" withPlaytime:@"4:00"];

        Song *cSong = [[Song alloc]initWithTitle:@"Hayate" withArtist:@"Spitz" withAlbum:@"Indigo Chiheisen" withPlaytime:@"4:21"];

        Song *dSong = [[Song alloc]initWithTitle:@"I have a Dreams" withArtist:@"WestLife" withAlbum:@"Season" withPlaytime:@"4:11"];

        Song *eSong = [[Song alloc]initWithTitle:@"What Do You Know" withArtist:@"David Choi" withAlbum:@"Tomorrow" withPlaytime:@"3:46"];


        //create playList

        Playlist *playlistA = [[Playlist alloc]initWithName:@"Playlist A"];

        Playlist *playListB = [[Playlist alloc]initWithName:@"Playlist B"];

    //store Song A & B to Playlist A and Song A,B,C to playlist B

        [playlistA addSong:aSong];

        [playlistA addSong:bSong];

        [playListB addSong:aSong];

        [playListB addSong:bSong];

        [playListB addSong:cSong];

//        [playListB removeSong:eSong];


//Creating Master Collection

        MusicCollection *myCollection = [[MusicCollection alloc]initWithName:@"Library"];

        [myCollection addPlaylist:playlistA];
        [myCollection addPlaylist:playListB];
        [myCollection addSong:eSong];
        [myCollection addSong:dSong];

        [myCollection removePlaylist:playListB];
        [myCollection removeSong:aSong];

        NSSet *container2 = [myCollection lookUpTitle:@"What"];

    NSLog(@"%@",container2);


    //    NSLog(@"%@",myCollection);
    }
    return 0;
}

-(instancetype) initWithName: (NSString *)aName{
    self = [super init];
    if (self) {

        self.name           = [NSMutableString stringWithString:aName];
        self.listOfPlaylists = [NSMutableArray array];
        self.masterSongs = [NSMutableSet set];


    }
    return self;
}

-(instancetype) init{

    return  [self initWithName:@""];

}

-(void) addPlaylist: (Playlist *)aPlayList{

    if ([listOfPlaylists containsObject:aPlayList]==YES) {

    }
    else
        [listOfPlaylists addObject:aPlayList];


}

-(void) removePlaylist: (Playlist *)aPlayList{
    if ([listOfPlaylists containsObject:aPlayList]) {

        [listOfPlaylists removeObjectIdenticalTo:aPlayList];
    }

    else{
        ;
    }

}

- (void) displaySong{

    NSLog(@"displaying all song in Collection");

    NSLog(@" %@",self.masterSongs);

}

- (void) addSong :(Song *)aSong{
    if (![masterSongs containsObject:aSong]) {

        [masterSongs addObject:aSong];

    }
}

- (void) removeSong: (NSString *)zSong{

    //remove from reference playlist


    NSSet *targets = [self lookUpTitle:zSong];

    if ([targets count]>0) {
        [self.masterSongs minusSet:targets];

        for (Playlist *playlist in listOfPlaylists) {
            // -all objects converts the set into array.

            [playlist.songList removeObjectsInArray:[targets allObjects]];
        }
    }
    else
        ;
}



 - (NSSet *) lookUpTitle: (NSString *)aName {

    NSString *filters = @"%K CONTAINS [cd] %@";
    NSPredicate *filter = [NSPredicate predicateWithFormat:filters, @"title", aName];

    NSSet *result = [masterSongs filteredSetUsingPredicate:filter];

    if ([result count] == 0) {
        NSLog(@"not found");

        return nil;
    }
    else{
        return result;
    }
}

- (void) addSong :(Song *)aSong{

    if (![songList containsObject:aSong]) {
        [songList addObject:aSong];
    }

}

- (void) removeSong: (Song *)aSong{
    if ([songList containsObject:aSong]){
    [self.songList removeObjectIdenticalTo:aSong];
    }
}
- (instancetype) initWithName: (NSString *)aPLName{
    self = [super init];

    if (self) {
        self.songList = [NSMutableArray array];
        self.playlistName = aPLName;
    }
    return self;
}

- (instancetype)init{
    return  [self initWithName:@""];
}

 - (instancetype) initWithTitle: (NSString *)aTitle withArtist: (NSString *)anArtist withAlbum: (NSString *)aAlbum withPlaytime: (NSString *)playingTime{

    self = [super init];

    if (self) {
        self.artist = [NSMutableString stringWithString:anArtist];
        self.album  = [NSMutableString stringWithString:aAlbum];
        self.title =   [NSMutableString stringWithString:aTitle];
        self.playtime = [NSMutableString stringWithString:playingTime];

    }
       return self;
}

-(instancetype) init{
    return  [self initWithTitle:@"null" withArtist:@"null" withAlbum:@"null" withPlaytime:@"null"];
}

---

您不需要使用

-predicateWithBlock

，在您的案例中使用以下谓词就足够了

[NSPredicate predicateWithFormat:@"SELF.title CONTAINS %@", @"Layla"];

编辑

Jeffery Thomas是对的，问题就在这一行——事实上编译器给出了警告

 [myCollection removeSong:aSong];

您正在向

-removeSong:

传递歌曲对象，而不是歌曲的标题。如果要传递到

-removeSong:

a

Song

对象，则将方法签名从

-（void）removeSong:（NSString*）songtile

更改为

-（void）removeSong:（Song*）Song

，并相应地更改方法实现以传递给谓词歌曲的标题，该标题是

NSString

- (void) removeSong: (Song *)zSong {

    //remove from reference playlist
    NSSet *targets = [self lookUpTitle:zSong.title];

    if ([targets count]>0) {
        [self.masterSongs minusSet:targets];

        for (Playlist *playlist in self.listOfPlaylists) {
            // -all objects converts the set into array.

            [playlist.songList removeObjectsInArray:[targets allObjects]];
        }
    }
}

---

从现在起，请不要忽略编译器警告，以避免在调试此类细微错误的过程中花费数天时间。

您不需要使用

-predicateWithBlock

，在您的情况下使用以下谓词就足够了

[NSPredicate predicateWithFormat:@"SELF.title CONTAINS %@", @"Layla"];

编辑

Jeffery Thomas是对的，问题就在这一行——事实上编译器给出了警告

 [myCollection removeSong:aSong];

您正在向

-removeSong:

传递歌曲对象，而不是歌曲的标题。如果要传递到

-removeSong:

a

Song

对象，则将方法签名从

-（void）removeSong:（NSString*）songtile

更改为

-（void）removeSong:（Song*）Song

，并相应地更改方法实现以传递给谓词歌曲的标题，该标题是

NSString

- (void) removeSong: (Song *)zSong {

    //remove from reference playlist
    NSSet *targets = [self lookUpTitle:zSong.title];

    if ([targets count]>0) {
        [self.masterSongs minusSet:targets];

        for (Playlist *playlist in self.listOfPlaylists) {
            // -all objects converts the set into array.

            [playlist.songList removeObjectsInArray:[targets allObjects]];
        }
    }
}

---

从现在起，请不要忽略编译器警告，以避免在调试此类细微错误的过程中花费数天时间。

您已经过多地理解了

-removeSong:

的含义，这已经给您带来了困惑。在

Playlist

，

-removeSong:

采用

歌曲

实例，但在

收藏

中，

-removeSong:

采用歌曲标题的

NSString

实例

问题是您将

歌曲的一个实例传递给需要
NSString
的版本

- (void)removeSong:(NSString *)zSong
{
    NSSet *targets = [self lookUpTitle:zSong];
    // …
}

应该是

- (void)removeSong:(Song *)aSong
{
    NSSet *targets = [self lookUpTitle:aSong.title];
    // …
}

或

我更改了方法的第二个版本的名称，以清楚地显示预期参数是什么。当您想使用第二个版本时，您会传递消息
[myCollection removeSongWithTitle:aSong.title]
您已经重载了
-removeSong:
的含义，这会造成您的混淆。在
Playlist
，
-removeSong:
采用
歌曲
实例，但在
收藏
中，
-removeSong:
采用歌曲标题的
NSString
实例

问题是您将
歌曲的一个实例传递给需要
NSString
的版本

- (void)removeSong:(NSString *)zSong
{
    NSSet *targets = [self lookUpTitle:zSong];
    // …
}

应该是

- (void)removeSong:(Song *)aSong
{
    NSSet *targets = [self lookUpTitle:aSong.title];
    // …
}

或

我更改了该方法第二个版本的名称，以清楚地显示所需的参数。当您想使用第二个版本时，您会传递消息
[myCollection removeSongWithTitle:aSong.title]
我也用它进行了测试，但它不起作用。Xcode仍然引发异常：由于未捕获的异常“NSInvalidArgumentException”而终止应用程序，原因：“无法对非字符串的内容执行子字符串操作。”。我知道masterSong本身包含Song对象，如果使用您建议的代码，它不会尝试用字符串过滤Song对象吗？您能更好地解释到底什么包含masterSong吗？你确定这是一个套餐吗