How to use static variables in Objective-C

Objective-CMediumStatic variablesThe usage is described in this article,Objective-CGlobal supportVariableThere are two main implementation methods: the first one is the same as in C/C ++, and the "extern" keyword is used; the other is the singleton implementation. For exampleVariablePut it in AppDelegate as a globalVariableAppDelegate is a singleton class)

In Objective-C, how does one implement static member variables like in C ++?

What you need to do is in the implementation (. m or. mm. In this way, you do not need to create A class A instance to access static variables in other classes. Although this static variable is not A static member variable of Class A, it achieves the same effect. The scope of static variables is limited to a single file. The code can be as follows:

 
 

  
  
//example.h     
  
  
@interface Example : NSObject {    
  
  
    
  
  
}    
  
  
    
  
  
- (id)init;    
  
  
+(int)instanceCount;    
  
  
    
  
  
@end    
  
  
    
  
  
//example.m     
  
  
#import "example.h"     
  
  
    
  
  
static int count;    
  
  
    
  
  
@implementation Example    
  
  
-(id)init{    
  
  
self = [super init];    
  
  
if(nil!=self){    
  
  
count+=1;    
  
  
}    
  
  
return self;    
  
  
}    
  
  
    
  
  
+(int)instanceCount{    
  
  
return count;    
  
  
}    
  
  
    
  
  
@end    
  
  
//example.h  
  
  
@interface Example : NSObject {  
  
  
 
  
  
}  
  
  
 
  
  
- (id)init;  
  
  
+(int)instanceCount;  
  
  
 
  
  
@end  
  
  
 
  
  
 
  
  
//example.m  
  
  
#import "example.h"  
  
  
 
  
  
static int count;  
  
  
 
  
  
@implementation Example  
  
  
-(id)init{  
  
  
self = [super init];  
  
  
if(nil!=self){  
  
  
count+=1;  
  
  
}  
  
  
return self;  
  
  
}  
  
  
 
  
  
+(int)instanceCount{  
  
  
return count;  
  
  
}  
  
  
@end 
 
 

In the above Example, you can use [Example instanceCount]Static variablesYou do not need to create an instance.

Summary: DetailsObjective-CMediumStatic variablesI hope this article will help you with the introduction of the usage method.