第二十七讲：Objective-C设计模式之单例
本帖最后由 Sian 于 2014-2-1 21:40 编辑单例，即全局变量
ThemeManager.h
//
//ThemeManager.h
//ThemeManager
//
//Created by yusian on 14-2-1.
//Copyright (c) 2014年 yusian. All rights reserved.
//
#import <Foundation/Foundation.h>
@interface ThemeManager : NSObject
@property (nonatomic, retain) NSString *name;
+ (id) sharedThemeManager;
@end
ThemeManager.m
//
//ThemeManager.m
//ThemeManager
//
//Created by yusian on 14-2-1.
//Copyright (c) 2014年 yusian. All rights reserved.
//
#import "ThemeManager.h"
@implementation ThemeManager
static ThemeManager *s;
+ (id) sharedThemeManager {
if (s == nil) {
s = [[ alloc] init];
}
return s;
}
- (id) init {
if (self = ) {
self.name = ;
}
return self;
}
- (NSString *) description {
return ;
}
- (void) dealloc {
;
_name = Nil;
;
}
@end
main.m
//
//main.m
//ThemeManager
//
//Created by yusian on 14-2-1.
//Copyright (c) 2014年 yusian. All rights reserved.
//
#import <Foundation/Foundation.h>
#import "ThemeManager.h"
int main(int argc, const char * argv[])
{
@autoreleasepool {
ThemeManager * tm = ;
ThemeManager * tm2 = ;
NSLog(@"tm is %@",tm);
NSLog(@"tm2 is %@",tm2);
NSLog(@"tm address is%p, tm2 address is %p",tm,tm2);
}
return 0;
}
运行结果：
2014-02-01 21:40:05.406 ThemeManager tm is My name is Default
2014-02-01 21:40:05.408 ThemeManager tm2 is My name is Default
2014-02-01 21:40:05.408 ThemeManager tm address is0x100301c00, tm2 address is 0x100301c00
Program ended with exit code: 0
典型的单例的写法：
+ (id) sharedThemeManager {
if (s == nil) {
s = [[ alloc] init];
}
return s;
}
加锁的写法：
+ (id) sharedThemeManager { @synchronized(self){ if (s == nil) { s = [[ alloc] init]; } } return s;}
GCD的写法：+ (id) sharedThemeManager { static dispatch_once_t onceToken; dispatch_once(&onceToken, ^{ if (s == nil) { s = [[ alloc] init]; } }); return s;}
重载的几个方法写法：
+ (id) copyWithZone: (NSZone *)zone { return self;}
- (id) retain { return self;}
- (oneway void) release {
}
- (NSUInteger) retainCount { return UINT_MAX;}
- (id) autorelease { return self;}
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