iPhone - writign可以被實例化多次類，每個實例都能夠訪問共享屬性

Question

我知道這可以用很多語言來完成的，但我不明白如何使用Objective-C這樣做。我已經讀過關於單身人士的消息，但是因爲他們被設計成只能實現一次，所以他們不會滿足這種需求。

所以這個類可以被稱爲是這樣的：

MyClass* obj1 = [[MyClass alloc] initWithKey:@"oneKey"]; 
NSString* lib = obj1.lib; 

或

int id = [MyClass idForKey:@"anotherKey"]; 

我試過這個代碼，但我敢肯定它是非常糟糕的，但我沒有看到如何實現這一點：

.h文件中

@interface MyClass : NSObject { 
    NSString* key; 
} 

@property(nonatomic, retain) NSString* key; 
@property(nonatomic, readonly) int id; 
@property(nonatomic, readonly) NSString* lib; 
@property(nonatomic, readonly) int value; 

+ (id) classWithKey:(NSString*)theKey; 

@end 

.m文件

#import "MyClass.h" 

@interface MyClass.h (Private) 
-(id)initWithKey:(NSString*)theKey; 
@end 

@implementation MyClass 

@synthesize key; 

static NSMutableDictionary* vars = nil; 


-(id)init 
{ 
    if (!(self = [super init])) return nil; 
    self.key = nil; 
    [MyClass initVars]; 
    return self; 
} 


-(id)initWithKey:(NSString*)theKey 
{ 
    if (!(self = [super init])) return nil; 
    self.key = theKey; 
    [MyClass initVars]; 
    return self; 
} 


+ (id) classWithKey:(NSString*) theKey 
{ 
    return [[[MyClass alloc] initWithKey:theKey] autorelease]; 
} 


+(void)initVars 
{ 
    if (vars != nil) return; 

#define mNum(x) [NSNumber numberWithInt:x] 
#define k0 @"id" 
#define k1 @"lib" 
#define k2 @"val" 

    vars = [NSMutableDictionary dictionary]; 
    [vars setObject:[NSDictionary dictionaryWithObjectsAndKeys:mNum(5), k0, @"One value", k1,  mNum(0), k2, nil] forKey:@"oneKey"]; 
    [vars setObject:[NSDictionary dictionaryWithObjectsAndKeys:mNum(8), k0, @"Another value", k1, mNum(1), k2, nil] forKey:@"anotherKey"]; 
    ... 

    [vars retain]; 
} 


- (int)id   { return [[[vars objectForKey:self.key] objectForKey:k0] intValue]; } 
- (NSString*)lib { return [[vars objectForKey:self.key] objectForKey:k1]; } 
- (int)value  { return [[[vars objectForKey:self.key] objectForKey:k2] intValue]; } 


-(void)dealloc 
{ 
    self.key = nil; 
    [vars release]; 
    [super dealloc]; 
} 

+(int) idForKey:(NSString*)theKey 
{ 
    if (vars == nil) [self initVars]; 
    return [[[vars objectForKey: theKey] objectForKey:k0] intValue]; 
} 

@end 

Answer 1

看看singleton類概念 有很多答案爲單身的，只是搜索

這裏是一個：

Is this really a singleton?