A singleton in IOS development

　　

A singleton is often used in iOS development, for example, each iOS program is itself a singleton, and a singleton is used, for example, to store personal preferences. So how do we write a singleton class on our own, with our own singleton object? Here is a single example of the code I wrote in the header file, this file is mainly some macros. The steps are written in detail, and arc or MRC can be used.

Singleton.h

Macro for a single case

/*

How to use

1: Include this header file

2: The name in the. h file that always contains Singleton_h (name) is the one you want to generate the singleton object in.

3: The name in the. m file that contains Singleton_m (name) is the one you want to generate the singleton object in.

Note that the name in step 2, 3 is consistent

4: Write init initialization method, because each singleton class initializes the content is different, so did not write to the macro inside, when creating a singleton class remember to write the Init method

5: Create singleton Object [class name Share+ (name)]

For example, we create a singleton for the person class: 1 Singleton_h (person) in person's. h file

2 Singleton_m (person) in the. m file of person

3 Write initialization method in the. m file of person

-(Instancetype) init{

static ID obj;

Static dispatch_once_t Oncetoken;

Dispatch_once (&oncetoken, ^{

if ((obj = [super init])) {

The initialization of this class is done here

}

});

self = obj;

return self;

}

}

4 contains the head file of this class of person in the place of use [person Shareperson];

# #: Connection Strings and Parameters

\: Indicates the next line is also the contents of the current row

*/

#ifndef Singleton_h

#define Singleton_h

#define SINGLETON_H (name) + (instancetype) share# #name;

#if __has_feature (OBJC_ARC)//Arc

#define SINGLETON_M (name) \

Static ID instance;\

+ (Instancetype) Allocwithzone: (struct _nszone *) zone{\

\

Static dispatch_once_t oncetoken;\

Dispatch_once (&oncetoken, ^{\

instance = [Super Allocwithzone:zone];\

});\

\

Return instance;\

}\

\

+ (instancetype) share# #name {\

return [[Self alloc]init];\

}\

+ (ID) copywithzone: (struct _nszone *) zone{\

Return instance;\

}

#else//Non-arc

#define SINGLETON_M (name) \

Static ID instance;\

+ (Instancetype) Allocwithzone: (struct _nszone *) zone{\

\

Static dispatch_once_t oncetoken;\

Dispatch_once (&oncetoken, ^{\

instance = [Super Allocwithzone:zone];\

});\

\

Return instance;\

}\

\

+ (instancetype) share# #name {\

return [[Self alloc]init];\

}\

\

-(OneWay void) release{\

\

\

}\

-(Instancetype) autorelease{\

Return instance;\

}\

\

-(Instancetype) retain{\

Return instance;\

}\

\

+ (ID) copywithzone: (struct _nszone *) zone{\

Return instance;\

}\

\

-(Nsuinteger) retaincount{\

Return 1;\

}

#endif

#endif

A singleton in IOS development