的NSMutableDictionary崩潰用「發送到不可變對象突變消息」

Question

我有具有NSMutableDictionary作爲屬性的類：

@interface Alibi : NSObject <NSCopying> 
@property (nonatomic, copy) NSMutableDictionary * alibiDetails; 
@end 

隨着下面的構造：

- (Alibi *)init 
{ 
    self = [super init]; 
    _alibiDetails = [NSMutableDictionary dictionary]; 
    return self; 
} 

和複印方法：

- (Alibi *)copyWithZone:(NSZone *)zone 
{ 
    Alibi *theCopy = [[Alibi alloc] init]; 
    theCopy.alibiDetails = [self.alibiDetails mutableCopy];  
    return theCopy; 
} 

當我嘗試呼叫setObject:ForKey:時，出現運行時錯誤mutating method sent to immutable object。

我有在視圖控制器中聲明的Alibi對象爲@property (copy, nonatomic) Alibi * theAlibi;，我用self.theAlibi = [[Alibi alloc] init];在viewDidLoad中初始化它。

出故障的線路是：

NSString * recipient; 
recipient = @"Boss"; 
[self.theAlibi.alibiDetails setObject:recipient forKey:@"Recipient"]; 

請讓我知道我在做什麼錯在這裏。我正在爲iPhone上的iOS 5編碼。

Answer 1

你有一個'copy'屬性，意思就是說 - 你的NSMutableDictionary將得到-copy方法，並且在被分配到綜合實例變量之前返回一個常規的NSDictionary。 This thread提供了一些關於解決這個問題的選項。

Answer 2

爲了完成這個線程，我將在下面包括我修改的Alibi類，這是我需要的。如果有人注意到任何內存泄漏或其他問題，那將不勝感激。

@implementation Alibi 

NSMutableDictionary *_details; 

- (Alibi *)init 
{ 
    self = [super init]; 
    _details = [NSMutableDictionary dictionary]; 
    return self; 
} 

- (NSMutableDictionary *)copyDetails 
{ 
    return [_details mutableCopy]; 
} 

- (NSMutableDictionary *)setDetails:(NSMutableDictionary *)value 
{ 
    _details = value; 
    return value; 
} 

- (void)addDetail:(id)value forKey:(id)key 
{ 
    [_details setObject:value forKey:key]; 
} 

- (id)getDetailForKey:(id)key 
{ 
    return [_details objectForKey:key]; 
} 

- (Alibi *)copyWithZone:(NSZone *)zone 
{ 
    Alibi *theCopy = [[Alibi alloc] init]; 

    theCopy.serverId = [self.serverId copyWithZone:zone]; 
    theCopy.user = [self.user copyWithZone:zone]; 
    theCopy.startTime = [self.startTime copyWithZone:zone]; 
    theCopy.endTime = [self.endTime copyWithZone:zone]; 
    [theCopy setDetails:[self copyDetails]]; 

    return theCopy; 
} 

@end