不能將超過3個對象添加到NSMutableSet

Question

使用一些字符串字段和一個浮點數創建了一個名為Item的自定義obj。

.h
        @interface Item : NSObject {

        NSString * name;        
        NSString * artNum;      
        NSString * collection;  
        NSString * description; 

        float num;

    }

    @property (nonatomic, copy) NSString * name;
    @property (nonatomic, copy) NSString * artNum;
    @property (nonatomic, copy) NSString * collection;
    @property (nonatomic, copy) NSString * description;
    @property (nonatomic) float num;

- (id)initWithName:(NSString *) name_ 
         andArtNum:(NSString *) artNum_
     andCollection:(NSString *) collection_
    andDescription:(NSString *) description_
          andNum:(float)num_;
- (id) init;
- (BOOL)isEqualToItem:(Item *)anItem;
- (NSUInteger)hash;

實施：

    #import "Item.h"


@implementation Item

@synthesize name;
@synthesize artNum;
@synthesize collection;
@synthesize description;
@synthesize num;

- (id)initWithName:(NSString *) name_ 
         andArtNum:(NSString *) artNum_
     andCollection:(NSString *) collection_
    andDescription:(NSString *) description_
          andNum:(float)num_
{
    if (self = [super init]) {
        self.name       = name_;
        self.artNum     = artNum_;
        self.collection = collection_;
        self.description= description_;
        self.num        = num_;
    }
    return self;
}

-(id)init{
    return [self initWithName:@"" 
                    andArtNum:@""        
                andCollection:@""
              andDescription :@""
                     andNum:.0];
}

- (void)dealloc {
    [name release];
    [artNum release];
    [collection release];
    [description release];
    [super dealloc];
}

- (BOOL)isEqual:(id)other {
    if (other == self)
        return YES;
    if (!other || ![other isKindOfClass:[self class]])
        return NO;
    return [self isEqualToItem:other];
}

- (BOOL)isEqualToItem:(Item *)anItem {
    if (self == anItem)
        return YES;
    if (![(id) self.name         isEqual:anItem.name])
        return NO;
    if (![(id) self.artNum       isEqual:anItem.artNum])
        return NO;
    if (![(id) self.collection   isEqual:anItem.collection])
        return NO;
    if (![(id) self.description  isEqual:anItem.description])
        return NO;
    if (!self.num == anItem.num)
        return NO;

//    if (![[self customObject] isEqualToCustomObject:[anItem customObject]])
//        return NO;
    return YES;
}

- (NSUInteger)hash {
    NSString *string4Hash = [NSString stringWithFormat:@"%@%@%@%@%f",self.name,self.artNum,self.collection,self.description,self.num];
    NSUInteger hash = [string4Hash hash];
    return hash;
}

@end

現在，我將NSMutableSet（屬於另一個類的屬項，屬性名）初始化為[[NSMutableSet alloc] init]，並且不能向其添加3個以上的Item對象。 而且BTW項目以非常奇怪的方式添加...

    -(IBAction) itemAdd:(id)sender{
    NSLog(@"itemAdded");
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
    Item *item = [[Item alloc] initWithName:lblItemName.text
                                  andArtNum:lblItemArt.text
                              andCollection:lblItemCollection.text
                                                         andDescription:lblItemDescriprion.text
                                   andNum:random()*100];
    [self.itemsAdded addObject:item];

    NSLog(@"itemAdd: intems added count: %i",[self.itemsAdded count]);
    for (Item *it in itemsAdded){
        NSLog(@"item added num is: %f",it.num);
    }
    [pool release];
}

這就是我得到的：

2012-03-28 20:22:49.479 MyApp[2493:207] itemAdded
2012-03-28 20:22:49.479 MyApp[2493:207] itemAdd: intems added count: 1
2012-03-28 20:22:49.479 MyApp[2493:207] item added num is: 40311868.000000
2012-03-28 20:22:51.175 MyApp[2493:207] itemAdded
2012-03-28 20:22:51.176 MyApp[2493:207] itemAdd: intems added count: 2
2012-03-28 20:22:51.176 MyApp[2493:207] item added num is: 40311868.000000
2012-03-28 20:22:51.176 MyApp[2493:207] item added num is: -1206257280.000000
2012-03-28 20:22:51.448 MyApp[2493:207] itemAdded
2012-03-28 20:22:51.448 MyApp[2493:207] itemAdd: intems added count: 2
2012-03-28 20:22:51.448 MyApp[2493:207] item added num is: 40311868.000000
2012-03-28 20:22:51.448 MyApp[2493:207] item added num is: -1206257280.000000
2012-03-28 20:22:51.623 MyApp[2493:207] itemAdded
2012-03-28 20:22:51.623 MyApp[2493:207] itemAdd: intems added count: 3
2012-03-28 20:22:51.623 MyApp[2493:207] item added num is: 40311868.000000
2012-03-28 20:22:51.623 MyApp[2493:207] item added num is: -335000352.000000
2012-03-28 20:22:51.624 MyApp[2493:207] item added num is: -1206257280.000000
2012-03-28 20:22:51.815 MyApp[2493:207] itemAdded
2012-03-28 20:22:51.816 MyApp[2493:207] itemAdd: intems added count: 3
2012-03-28 20:22:51.816 MyApp[2493:207] item added num is: 40311868.000000
2012-03-28 20:22:51.816 MyApp[2493:207] item added num is: -335000352.000000
2012-03-28 20:22:51.816 MyApp[2493:207] item added num is: -1206257280.000000
2012-03-28 20:22:51.991 MyApp[2493:207] itemAdded
2012-03-28 20:22:51.992 MyApp[2493:207] itemAdd: intems added count: 3
2012-03-28 20:22:51.992 MyApp[2493:207] item added num is: 40311868.000000
2012-03-28 20:22:51.992 MyApp[2493:207] item added num is: -335000352.000000
2012-03-28 20:22:51.992 MyApp[2493:207] item added num is: -1206257280.000000
2012-03-28 20:22:52.175 MyApp[2493:207] itemAdded
2012-03-28 20:22:52.175 MyApp[2493:207] itemAdd: intems added count: 3
2012-03-28 20:22:52.175 MyApp[2493:207] item added num is: 40311868.000000
2012-03-28 20:22:52.175 MyApp[2493:207] item added num is: -335000352.000000
2012-03-28 20:22:52.176 MyApp[2493:207] item added num is: -1206257280.000000
2012-03-28 20:22:52.360 MyApp[2493:207] itemAdded
2012-03-28 20:22:52.361 MyApp[2493:207] itemAdd: intems added count: 3
2012-03-28 20:22:52.361 MyApp[2493:207] item added num is: 40311868.000000
2012-03-28 20:22:52.361 MyApp[2493:207] item added num is: -335000352.000000
2012-03-28 20:22:52.361 MyApp[2493:207] item added num is: -1206257280.000000
2012-03-28 20:22:52.591 MyApp[2493:207] itemAdded
2012-03-28 20:22:52.591 MyApp[2493:207] itemAdd: intems added count: 3
2012-03-28 20:22:52.592 MyApp[2493:207] item added num is: 40311868.000000
2012-03-28 20:22:52.592 MyApp[2493:207] item added num is: -335000352.000000
2012-03-28 20:22:52.592 MyApp[2493:207] item added num is: -1206257280.000000

看一看有2次打印，該打印有2個項目，但此時必須有3個項目。 它可以隨機工作，並且可以打印2次以上兩次。 同樣，添加超過3個項目也沒有反應。 只有3個物品可以永久存在4個。 這是為什么？ 我做錯了什么？

Answer 1

如果創建相同的對象，則僅將一個副本放入集合中。

這是設計使然。 如果要多個副本，請改用數組。

但是，這可能比您預期的要發生的更多，因為您使用的是random變量，並且沒有正確植入種子。 如果希望它不經常發生，請使用arc4random() % 100 （或大於100的數字），或者使用其他一些變量來使對象不相同，這樣您就可以解決此問題。

編輯：

您遇到的另一個問題是以下代碼行：

if (!self.num == anItem.num)

為了進行適當的測試，請將其更改為：

if (self.num != anItem.num)

（否則，您將BOOL！self.num與float anItem.num進行比較）

Answer 2

我在您的IBAction中的代碼中有一些評論：

1. 首先，您不需要NSAutoreleasePool，而要釋放池，您必須執行以下操作：[池排水]

2. 您確定要通過alloc init或alloc initWithCapacity來聲明您的NSMutableSet！

3. 我建議你NSMutableArray

4. 添加到MutableArray中后，請不要放開您的物品

希望對您有幫助