MRC環(huán)境-單例實(shí)現(xiàn)

.h文件實(shí)現(xiàn)

@interface DemoSoundTool : NSObject
+ (instancetype)sharedSoundTool;

.m文件實(shí)現(xiàn)

實(shí)現(xiàn)一個(gè)類方法
重寫五個(gè)系統(tǒng)方法

#import "DemoSoundTool.h"

@implementation DemoSoundTool

static DemoSoundTool *_soundTool = nil;

/**
 *  alloc方法內(nèi)部會(huì)調(diào)用allocWithZone:
 *  zone : 系統(tǒng)分配給app的內(nèi)存
 */
+ (id)allocWithZone:(struct _NSZone *)zone
{
    if (_soundTool == nil) {
        static dispatch_once_t onceToken;
        dispatch_once(&onceToken, ^{ // 安全(這個(gè)代碼只會(huì)被調(diào)用一次)
            _soundTool = [super allocWithZone:zone];
        });
    }
    return _soundTool;
}

- (id)init
{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        _soundTool = [super init];
    });
    return _soundTool;
}

+ (instancetype)sharedSoundTool
{
    return [[self alloc] init];
}

- (oneway void)release
{

}

- (id)retain
{
    return self;
}

- (NSUInteger)retainCount
{
    return 1;
}

ARC環(huán)境下- 單例實(shí)現(xiàn)

不重寫 release, retain, retainCount這三個(gè)函數(shù)即可, 其他 和 MRC一樣

當(dāng)需要定義多個(gè) 單例的時(shí)候, 每個(gè)單例內(nèi)部實(shí)現(xiàn)基本一樣, 這時(shí)可以[ 抽取一個(gè)宏 ] 實(shí)現(xiàn)單例, 減少代碼量開支

定義一個(gè)頭文件singleton.h

// 幫助實(shí)現(xiàn)單例設(shè)計(jì)模式

// .h文件的實(shí)現(xiàn)
#define SingletonH(methodName) + (instancetype)shared##methodName;

// .m文件的實(shí)現(xiàn)
#if __has_feature(objc_arc) // 是ARC
#define SingletonM(methodName) \
static id _instace = nil; \
+ (id)allocWithZone:(struct _NSZone *)zone \
{ \
if (_instace == nil) { \
static dispatch_once_t onceToken; \
dispatch_once(&onceToken, ^{ \
_instace = [super allocWithZone:zone]; \
}); \
} \
return _instace; \
} \
\
- (id)init \
{ \
static dispatch_once_t onceToken; \
dispatch_once(&onceToken, ^{ \
_instace = [super init]; \
}); \
return _instace; \
} \
\
+ (instancetype)shared##methodName \
{ \
return [[self alloc] init]; \
} \
+ (id)copyWithZone:(struct _NSZone *)zone \
{ \
return _instace; \
} \
\
+ (id)mutableCopyWithZone:(struct _NSZone *)zone \
{ \
return _instace; \
}

#else // 不是ARC

#define SingletonM(methodName) \
static id _instace = nil; \
+ (id)allocWithZone:(struct _NSZone *)zone \
{ \
if (_instace == nil) { \
static dispatch_once_t onceToken; \
dispatch_once(&onceToken, ^{ \
_instace = [super allocWithZone:zone]; \
}); \
} \
return _instace; \
} \
\
- (id)init \
{ \
static dispatch_once_t onceToken; \
dispatch_once(&onceToken, ^{ \
_instace = [super init]; \
}); \
return _instace; \
} \
\
+ (instancetype)shared##methodName \
{ \
return [[self alloc] init]; \
} \
\
- (oneway void)release \
{ \
\
} \
\
- (id)retain \
{ \
return self; \
} \
\
- (NSUInteger)retainCount \
{ \
return 1; \
} \
+ (id)copyWithZone:(struct _NSZone *)zone \
{ \
    return _instace; \
} \
 \
+ (id)mutableCopyWithZone:(struct _NSZone *)zone \
{ \
    return _instace; \
}

#endif

宏定義之后,就可以一句話搞定 單例

例如在MRC環(huán)境下 , 單例模式可以這樣實(shí)現(xiàn)

.h文件實(shí)現(xiàn)

#import "Singleton.h"
@interface DemoSoundTool : NSObject

SingletonH(SoundTool)

.m文件實(shí)現(xiàn)

#import "Singleton.h"
#import "DemoSoundTool.h"

@implementation DemoSoundTool

//這樣一句話就搞定了
SingletonM(SoundTool)

@end