详解IOS 单例的两种方式

详解ios 单例的两种方式

方法一：

#pragma mark - 
#pragma mark sharedsingleton methods 
 
//单例函数 
static rtdatamodel *sharedsingletonmanager = nil; 
 
+ (rtdatamodel *)sharedmanager 
{ 
  @synchronized(self) { 
    if (sharedsingletonmanager == nil) { 
      sharedsingletonmanager = [[self alloc] init]; 
    } 
  } 
  return sharedsingletonmanager; 
} 
 
+ (id)allocwithzone:(nszone *)zone 
{ 
  @synchronized(self) { 
    if (sharedsingletonmanager == nil) { 
      sharedsingletonmanager = [super allocwithzone:zone]; 
      return sharedsingletonmanager; // assignment and return on first allocation 
    } 
  } 
  return nil; //on subsequent allocation attempts return nil 
} 
 
- (id)copywithzone:(nszone *)zone 
{ 
  return sharedsingletonmanager; 
} 
 
- (id)retain 
{ 
  return sharedsingletonmanager; 
} 
 
- (nsuinteger)retaincount 
{ 
  return uint_max; //denotes an object that cannot be released 
} 
 
- (oneway void)release 
{ 
  //do nothing 
} 
 
- (id)autorelease 
{ 
  return sharedsingletonmanager; 
} 
 
//单例函数结束 

方法二：

.h文件

#import <foundation/foundation.h> 
 
@interface rttestdatamodel : nsobject 
{ 
  nsmutablearray      * _buydatatarray; 
  nsmutablearray      * _selldatatarray; 
} 
 
+ (rttestdatamodel *)sharedmanager; 
 
- (void)addoptionbuydataarraymodel: (nsmutablearray *)dataarray; 
- (nsmutablearray *)getoptionbuydataarraymodel; 
 
@end 

.m文件

#import "rttestdatamodel.h" 
 
@implementation rttestdatamodel 
 
+ (rttestdatamodel *)sharedmanager 
{ 
  static rttestdatamodel *sharedmanager = nil; 
  static dispatch_once_t predicate; 
   
  dispatch_once(&predicate,^{ 
    sharedmanager = [[rttestdatamodel alloc]init]; 
  }); 
 
  return sharedmanager; 
} 
 
- (void)dealloc 
{ 
  [_buydatatarray removeallobjects]; 
  [_buydatatarray release]; 
   
  [super dealloc]; 
} 
 
- (id)init 
{ 
  self = [super init]; 
   
  if (self != nil) { 
    _buydatatarray = [[nsmutablearray alloc] initwithcapacity:8]; 
  } 
  return self; 
} 
 
- (void)addoptionbuydataarraymodel: (nsmutablearray *)dataarray{ 
   
  if (dataarray != nil) { 
     
    [_buydatatarray removeallobjects]; 
    [_buydatatarray addobjectsfromarray:dataarray]; 
  } 
} 
 
- (nsmutablearray *)getoptionbuydataarraymodel{ 
   
  return _buydatatarray; 
} 
@end 

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