iOS单例模式

- 3 mins
Objective-C Swift

不说单例模式，只是总结下实现。

Swift 单例模式

全局变量方法

private let sharedKraken = TheOneAndOnlyKraken()
class TheOneAndOnlyKraken {
    class var sharedInstance: TheOneAndOnlyKraken {
        return sharedKraken
    }
}

单行单例法

class TheOneAndOnlyKraken {
    static let sharedInstance = TheOneAndOnlyKraken()
}

使用时不要忘记设置初始化方法为私有

class TheOneAndOnlyKraken {
    static let sharedInstance = TheOneAndOnlyKraken()
    private init() {} //This prevents others from using the default '()' initializer for this class.
}

Objective-C 单例模式

ARC单例模式

//.h文件
#import <Foundation/Foundation.h>
@interface Singleton : NSObject
//单例方法
+(instancetype)sharedSingleton;
@end

//.m文件
#import "Singleton.h"
@implementation Singleton
//全局变量
static id _instance = nil;
//单例方法
+(instancetype)sharedSingleton{
    return [[self alloc] init];
}
////alloc会调用allocWithZone:
+(instancetype)allocWithZone:(struct _NSZone *)zone{
    //只进行一次
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        _instance = [super allocWithZone:zone];
    });
    return _instance;
}
//初始化方法
- (instancetype)init{
    // 只进行一次
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        _instance = [super init];
    });
    return _instance;
}
//copy在底层 会调用copyWithZone:
- (id)copyWithZone:(NSZone *)zone{
    return  _instance;
}
+ (id)copyWithZone:(struct _NSZone *)zone{
    return  _instance;
}
+ (id)mutableCopyWithZone:(struct _NSZone *)zone{
    return _instance;
}
- (id)mutableCopyWithZone:(NSZone *)zone{
    return _instance;
}
@end

MRC中的单例实现

//.h文件
#import <Foundation/Foundation.h>
//单例方法
@interface Singleton : NSObject
+ (instancetype)sharedSingleton;
@end

//.m文件
#import "Singleton.h"
@implementation Singleton
//全局变量
static id _instance = nil;
//单例方法
+(instancetype)sharedSingleton{
    //系统的大多数类方法都有做autorelease，所以我们也需要做一下
     return [[[self alloc] init] autorelease];
}
//alloc会调用allocWithZone:
+(instancetype)allocWithZone:(struct _NSZone *)zone{
    //只进行一次
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        _instance = [super allocWithZone:zone];
    });
    return _instance;
}
//初始化方法
-(instancetype)init{
    // 只进行一次
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        _instance = [super init];
    });
    return _instance;
}
- (oneway void)release{
    //什么都不做 保证单例对象不被销毁
}
//返回本身 保证只有一个单例对象
- (instancetype)retain{
    return _instance;
}
//计数器为1 保证只有一个单例对象
- (NSUInteger)retainCount{
    return 1;
}
//copy在底层 会调用copyWithZone:
+ (id)copyWithZone:(struct _NSZone *)zone{
    return  _instance;
}
- (id)copyWithZone:(NSZone *)zone{
    return _instance;
}
+ (id)mutableCopyWithZone:(struct _NSZone *)zone{
    return _instance;
}
- (id)mutableCopyWithZone:(NSZone *)zone{
    return _instance;
}
@end

整理成了宏定义(ARC,MRC)

// ## : 连接字符串和参数
#define singleton_h(name) + (instancetype)shared##name;
#if __has_feature(objc_arc) // ARC
#define singleton_m(name) \
static id _instance; \
+ (id)allocWithZone:(struct _NSZone *)zone \
   { \
     static dispatch_once_t onceToken; \
     dispatch_once(&onceToken, ^{ \
    _instance = [super allocWithZone:zone]; \
   }); \
  return _instance; \
   } \
+ (instancetype)shared##name \
   { \
   static dispatch_once_t onceToken; \
   dispatch_once(&onceToken, ^{ \
   _instance = [[self alloc] init]; \
   });\
   return _instance; \
  } \
+ (id)copyWithZone:(struct _NSZone *)zone \
  { \
  return _instance; \
  }
#else // 非ARC
#define singleton_m(name) \
static id _instance; \
+ (id)allocWithZone:(struct _NSZone *)zone \
  { \
  static dispatch_once_t onceToken; \
  dispatch_once(&onceToken, ^{ \
  _instance = [super allocWithZone:zone]; \
  }); \
  return _instance; \
  } \
   \
+ (instancetype)shared##name \
     { \
     static dispatch_once_t onceToken; \
     dispatch_once(&onceToken, ^{ \
     _instance = [[self alloc] init]; \
     }); \
      return _instance; \
     } \
     \
- (oneway void)release \
    { \
       \
    } \
     \
- (id)autorelease \
  { \
   return _instance; \
  } \
    \
- (id)retain \
  { \
   return _instance; \
  } \
     \
- (NSUInteger)retainCount \
  { \
  return 1; \
  } \
    \
+ (id)copyWithZone:(struct _NSZone *)zone \
  { \
   return _instance; \
  }
#endif

宏定义使用

.h 文件

singleton_h(SoundTool)

.m 文件

singleton_m(SoundTool)
- (instancetype)init {
    if (self = [super init])
    {
        static dispatch_once_t onceToken;
        dispatch_once(&onceToken, ^{
            // 加载资源
        });
    }
    return self;
}

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