iOS uses a macro to write a single example

This article only describes the single case of Arc

The past has not been back down how to write a single case, that is, know this, but also know through the macro to write a single case, but can not remember, today to record

-(void) viewdidload {[Super viewdidload];    Siperson *person = [[Siperson alloc] init];    NSLog (@ "%@", person);    Siperson *person1 = [[Siperson alloc] init]; NSLog (@ "%@", Person1);}

Create person, print, actually 2 objects. No problem.

Create a method

 #import   "SIPerson.h" static siperson *instance_ = nil;@ implementation siperson///Method 1, quickly create object +  (instancetype) sharedinstance{    static  dispatch_once_t oncetoken;    dispatch_once (&onceToken, ^{         instance_ = [[self alloc] init];     });     return instance_;} Method 2. This method must have, that is alloc] init] method, will be called this method +  (instancetype) Allocwithzone: (struct _nszone *) Zone{    static dispatch_once_t oncetoken;    dispatch_once ( &onceToken, ^{        instance_ = [super  allocwithzone:zone];    });     return instance_;} @end//There should also be a + copy method, because it might be copy, then it is possible to generate a new method 

Method 12 must be implemented in order to be a singleton. If Method 2 is not implemented, sharedInstance the implementation is really a singleton, but by alloc] init] having another object generated

2016-09-17 14:17:45.086 sharedinstance[9158:611161] 2016-09-17 14:17:45.087 sharedinstance[9158:611161]

If your object is likely to be called in the future copy (the protocol should be declared), you should also implement a method

-(ID) Copywithzone: (Nszone *) zone{return instance_;}

Copy of the time, is generally generated a new object, so it is not a single case, but the use of less, not particularly needed, can not implement this method, for Mao to write this way? Because he's the object method, instance_ there's a value inside.

[Super Viewdidload];    Siperson *person = [Siperson sharedinstance];    NSLog (@ "%@", person);    Siperson *person1 = [[Siperson alloc] init];        NSLog (@ "%@", Person1);    Siperson *person2 = [Person1 copy]; NSLog (@ "%@", Person2);

The results are as follows

2016-09-17 14:24:10.555 sharedinstance[9199:615987] 2016-09-17 14:24:10.555 sharedinstance[9199:615987] 2016-09-17 14:24:10.556 sharedinstance[9199:615987]

/** *   macros defined in the. h file, Arc * *  sisingletonh (name)   This is a macro  *  +   (instancetype) shared# #name; This is a substituted method,  # #代表着shared +name  highly customizable  *  outside we use   " Sisingletonh (Gege)   then in the. h file, a method "+  (instancetype) sharedgege" is defined, so the first letter is capitalized  * *    @return   A well-done method name  */#define  SISINGLETONH (name)  +  (instancetype) shared# #name;/**  *   macro  arc * *  sisingletonm (name) in. m files   This is a macro, because it's a multi-line thing, So there is a "\" behind each line, except for the last line, *  to pass a "name" because there is a way to name "+  (instancetype) shared# #name"  *    @return   Simple Interest  */#define  SISINGLETONM (name)  static siperson *instance_ =  nil;+  (instancetype) shared# #name {    static dispatch_once_t oncetoken ;     dispatch_once (&onceToken, ^{         Instance_ = [[self alloc] init];    });     return instance_;} +  (Instancetype) Allocwithzone: (struct _nszone *) zone{    static  Dispatch_once_t oncetoken;    dispatch_once (&onceToken, ^{         instance_ = [super allocwithzone:zone];    }) ;     return instance_;} -  (ID) Copywithzone: (nszone *) Zone{    return instance_;}

Actual use

. h file Sisingletonh (Default)

. m file Sisingletonm (Default)

is a sentence, there is no symbol (when the definition of the symbol), it is so simple

In the actual use of the time

[Super Viewdidload];    Siperson *person = [Siperson Shareddefault];    NSLog (@ "%@", person);    Siperson *person1 = [[Siperson alloc] init];    NSLog (@ "%@", Person1);    Siperson *person2 = [Person1 copy]; NSLog (@ "%@", person2);//Print results 2016-09-17 14:56:39.508 sharedinstance[9292:633076] 2016-09-17 14:56:39.508 SHAREDINSTANCE[9292:633076] 2016-09-17 14:56:39.508 sharedinstance[9292:633076]

The file address you can use to get it.

Simply say how to define a swift version of a single case, normal writing, no study of single cases

iOS uses a macro to write a single example