如何在NSObject實例中爲我的自定義鍵（undefinedKey）設置一個值？

Question

我已經子類NSObject。我需要將一個對象（NSMutableArray實例）設置爲該類的實例的未定義​​鍵（@"ItemsList"）。我怎樣才能做到這一點？例如，我想設置，

[myObject setValue:myArray forUndefinedKey:@"ItemsList"]; 

我應該怎麼做才能做到這一點？

Answer 1

這裏有一個方法可以輕鬆地做到這一點「而無需創建高德」：

@interface MONObject : NSObject 
{ 
    NSMutableDictionary * stuff; 
} 
// .... 
- (void)setValue:(id)value forCustomKey:(NSString *)key; 

@end 

@implementation MONObject 

- (void)setValue:(id)value forCustomKey:(NSString *)key 
{ 
    assert(self.stuff && value && key); 
    [self.stuff setValue:value forKey:key]; 
} 

@end 

Answer 2

您可以使用這樣一個類，繼承它。 （請參閱下面的子類，並注意 testProperty是如何不被合成，除了被用作動態）

@interface INDynamicPersister : NSObject { 

} 

/*! 
    @method  saveObject:forKey: 
    @abstract Invoked when a property setter is invoked. 
*/ 
- (void) saveObject:(id)value forKey:(NSString *)key; 


/*! 
    @method  retrieveObjectForKey: 
    @abstract Invoked when a property getter needs its value. 
*/ 
- (id) retrieveObjectForKey:(NSString *)key; 

@end 


#define Property_Setter_Suffix @":" 

@implementation INDynamicPersister 

- (NSMethodSignature *)methodSignatureForSelector:(SEL)sel { 

    NSMethodSignature *signature = [super methodSignatureForSelector:sel]; 

    if (signature == nil) { 
     // get the name of the selector 
     NSString *selectorName = [NSStringFromSelector(sel) lowercaseString]; 

     // if we have a setter property ... 
     if ([selectorName hasSuffix:Property_Setter_Suffix]) { 
      signature = [NSMethodSignature signatureWithObjCTypes:"v@:@"]; 
     } 
     else { 
      signature = [NSMethodSignature signatureWithObjCTypes:"@@:"]; 
     } 
    } 

    return signature; 
} 

/*! 
    @method  forwardInvocation: 
    @abstract This method will handle the invocation for the property getters and setters. 
*/ 
- (void)forwardInvocation:(NSInvocation *)anInvocation { 

    // get the name of the selector 
    NSString *selectorName = [NSStringFromSelector([anInvocation selector]) lowercaseString]; 

    // if we have a setter property ... 
    if ([selectorName hasSuffix:Property_Setter_Suffix]) { 
     int selectorLength = [selectorName length]; 

     NSString *propertyName = [selectorName substringWithRange:NSMakeRange(3, selectorLength - 4)]; 

     // get the value of the invocation 
     id invocationValue; 
     [anInvocation getArgument:&invocationValue atIndex:2]; 

     // now set the value for the property 
     [self saveObject:invocationValue forKey:propertyName]; 
    } 
    else { 
     // if we have a getter property ... 
     id invocationReturnValue = [self retrieveObjectForKey:selectorName]; 

     [anInvocation setReturnValue:&invocationReturnValue]; 
    } 
} 

- (void) saveObject:(id)value forKey:(NSString *)key { 
    [NSException raise:@"NotImplementedException" format:@"You need to override this method"]; 
} 

- (id) retrieveObjectForKey:(NSString *)key { 
    [NSException raise:@"NotImplementedException" format:@"You need to override this method"]; 

    return nil; // compiler is happy now 
} 


@end 

子類可能是與此類似：

@interface MyDynamicEntity : INDynamicPersister { 
    NSMutableDictionary *propertyValues; 
} 

@property (retain, nonatomic) NSString * testProperty; 

@end 


@implementation MyDynamicEntity 

@dynamic testProperty; 

- (id) init { 
    if (self = [super init]) { 
     propertyValues = [[NSMutableDictionary alloc] init]; 
    } 

    return self; 
} 

- (void) dealloc { 
    [propertyValues release], propertyValues = nil; 

    [super dealloc]; 
} 

- (void) saveObject:(id)value forKey:(NSString *)key { 
    if (!value) { 
     [propertyValues removeObjectForKey:key]; 
    } 
    else { 
     [propertyValues setObject:value forKey:key]; 
    } 
} 

- (id) retrieveObjectForKey:(NSString *)key { 
    return [propertyValues objectForKey:key]; 
} 

@end 

希望這有助於:)

Answer 3

@interface MyObject : NSObject 

@end 

@implementation MyObject { 
    NSMutableDictionary*itemsList; 
} 
- (id)valueForUndefinedKey:(NSString*)key { 
    if ([key isEqualToString:@"itemsList"]) { 
     return itemsList; 
    } 
    else { 
     return [super valueForUndefinedKey:key]; 
    } 
} 

- (void)setValue:(id)value forUndefinedKey:(NSString*)key { 

    if ([key isEqualToString:@"itemsList"]) { 
     itemsList = value; 
    } 
    else { 
     [super setValue:value forUndefinedKey:key]; 
    } 
} 
@end 

以及調用屬性，有必要通過valueForKey叫它：

MyObject*myObject = [MyObject new]; 
[myObject setValue:@[@"item1", @"item2"] forKey:@"itemsList"]; 
NSArray*itemsList = [myObject valueForKey:@"itemsList"];