Objective-C ::使用方法更改对象

Question

我有一个名为“CardSet”的类，其中包含一个用于容纳“卡片”的NSMutableArray * cardSet，我将其扩展为制作“DeckCards”。我想要“CardSet”有一个名为“（void）addCard：（Card *）”（以及类似的方法“removeCard”）的方法。我想要“addCard”，以便如何访问并设置cardSet。更好的是，我想使用“addCard”方法初始化cardSet。类文件 “CardSet.h” 记载：

#import <Cocoa/Cocoa.h> 

#import <Card.h> 

@interface CardSet : NSObject { 

    NSMutableArray* cardSet; 

} 

-(id)init; 

-(NSMutableArray*)getCardSet; 

-(void)setCardSet:(NSMutableArray *)new_cardset; 

-(Card*)getCard:(NSInteger) index; 

**-(void)addCard:(Card*) new_card;** 

-(void)removeCard:(Card*) old_card; 

-(void)dealloc; 

@property (readwrite, retain, getter=getCardSet, setter=setCardSet) NSMutableArray* cardSet; 

@end 

和方法文件读取：

#import "CardSet.h" 

@implementation CardSet 

-(id)init{ 
    if(self = [super init]){} //will add initialisations here later 
    return self; 
} 

-(NSMutableArray*)getCardSet{ 
    return cardSet; 
} 

-(void)setCardSet:(NSMutableArray *)new_cardSet{ 
    cardSet = new_cardSet; 
} 

-(Card*)getCard:(NSInteger)index{ 
    return [cardSet objectAtIndex:index]; 
} 

**-(void)addCard:(Card *)new_card{ 
    [cardSet addObject:new_card]; 
}** 

-(void)removeCard:(Card *)old_card{ 
    [cardSet removeObject:old_card]; 
} 

-(void)dealloc{ 
    [cardSet release]; 
    [super dealloc]; 
} 

@synthesize cardSet; 

@end 

这编译就好了。我想用它的“addCard”方法初始化一个“DeckCards”实例52次。当我在DeckCards setter方法中调用addCard 52次并询问其“cardSet”的大小时，我返回0.

这似乎是一个范围或特权问题？ “addCard”方法是否具有setter特权？必须使用setter参数与返回和相应的成员类型相同？

[我可以通过在“DeckCard”之外创建一个NSMutableArray对象“deck_cards_temp”来解决上述问题，向其中添加52张卡片，并通过setter继承“DeckCards” CardSet”。这是不是很满意！]

你有什么建议？非常感谢您的帮助和耐心。

Answer 1

你永远不会实际创建cardSet对象。你应该在你-init方法来创建它：

-(id)init 
{ 
    if(self = [super init]) 
    { 
     cardSet = [[NSMutableArray alloc] init]; 
    } 
    return self; 
} 

因为你从来没有真正创建磁盘阵列，所有-addCard:的呼叫被发送给nil对象。

当您将一个数组传递给-setCardSet:时，您传递的是初始化数组，因此该数组不再为零，并且-addCard:调用正常工作。

Answer 2

CardSet.h

#import <Cocoa/Cocoa.h> 

// For know we just need to know there is a class named "Card" being used but implemented later 
@class Card; 

@interface CardSet : NSObject { 
    NSMutableArray *cardSet; 
} 

// Here are the methods according to "correct" naming conventions 
- (Card *)cardAtIndex:(NSInteger)index; 
- (void)addCard:(Card *)card; 
- (void)removeCard:(Card *)card; 

// This will help us and forget about writing the setter/getter 
@property (nonatomic, retain) NSMutableArray *cardSet; 

@end 

CardSet.m

#import "CardSet.h" 
// Now we tell the compiler what "Card" is and what methods etc. it has 
#import "Card.h" 

@implementation CardSet 

@synthesize cardSet; 

- (id)init { 
    if (self = [super init]) { 
     // If we don't create the cardSet, how are we able to work with it!? 
     NSMutableArray *anArray = [[NSMutableArray alloc] init]; 
     self.cardSet = anArray; 
     [anArray release]; 
    } 
    return self; 
} 

- (Card *)cardAtIndex:(NSInteger)index { 
    return [cardSet objectAtIndex:index]; 
} 

- (void)addCard:(Card *)card { 
    [cardSet addObject:card]; 
} 

- (void)removeCard:(Card *)card { 
    [cardSet removeObject:card]; 
} 

- (void)dealloc { 
    [cardSet release]; 
    [super dealloc]; 
} 

@end 

正如Abizern已经指出：命名的数组一样类是一件坏事。

Answer 3

我会缩短该init方法：

- (id)init { 
    if (self = [super init]) { 
     // If we don't create the cardSet, how are we able to work with it!? 
     self.cardSet = [NSMutableArray array]; 
    } 
    return self; 
}