不能将超过3个对象添加到NSMutableSet

Question

使用一些字符串字段和一个浮点数创建了一个名为Item的自定义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;

实施：

    #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

现在，我将NSMutableSet（属于另一个类的属项，属性名）初始化为[[NSMutableSet alloc] init]，并且不能向其添加3个以上的Item对象。 而且BTW项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];
}

这就是我得到的：

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，该打印有2个项目，但此时必须有3个项目。 它可以随机工作，并且可以打印2次以上两次。 同样，添加超过3个项目也没有反应。 只有3个物品可以永久存在4个。 这是为什么？ 我做错了什么？

Answer 1

如果创建相同的对象，则仅将一个副本放入集合中。

这是设计使然。 如果要多个副本，请改用数组。

但是，这可能比您预期的要发生的更多，因为您使用的是random变量，并且没有正确植入种子。 如果希望它不经常发生，请使用arc4random() % 100 （或大于100的数字），或者使用其他一些变量来使对象不相同，这样您就可以解决此问题。

编辑：

您遇到的另一个问题是以下代码行：

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

为了进行适当的测试，请将其更改为：

if (self.num != anItem.num)

（否则，您将BOOL！self.num与float anItem.num进行比较）

Answer 2

我在您的IBAction中的代码中有一些评论：

1. 首先，您不需要NSAutoreleasePool，而要释放池，您必须执行以下操作：[池排水]

2. 您确定要通过alloc init或alloc initWithCapacity来声明您的NSMutableSet！

3. 我建议你NSMutableArray

4. 添加到MutableArray中后，请不要放开您的物品

希望对您有帮助