passing the static variable as an argument->Objective C

c++ code
--------
#include "stdafx.h"
#include <iostream>
using namespace std;
class A
{
public:
    static int a;
    void set(int s)开发者_如何学Go
    {
     a=s;
     cout<<a<<endl;
    }
    void setData(int f)
    {
     cout<<"I am "<<f<<" years old!!!"<<endl;
    }
};
int A::a=0;
int main()
{
    A* ab=new A();
    ab->set(10);
    ab->setData(ab->a);
    return 0;
}

I am trying to get the same output for this equivalent Objective C code.

main.m
---------

#import <Foundation/Foundation.h>
#import "A.h"
int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    A* ab = [[A alloc]init];
    [ab set:10];
    [ab setData:ab.a]; //getting error when passed ab->a or ab.a as an argument
    [pool drain];
    return 0;
}

A.h
---

#import <Foundation/Foundation.h>

@interface A : NSObject {

}

-(void)set:(int)s;
-(void)setData:(int)f;

@end

A.m
----

#import "A.h"


@implementation A
static int a;
-(void)set:(int)s
{
    a=s;
    NSLog(@"%d\n",a);
}
-(void)setData:(int)f
{
    NSLog(@"%d",f);
}
@end

Error:Request for member 'a' in something not a structure or union.

---

There are no static instance variables or methods in Objective C. What you want can be done with class methods and static file scope variables. Class methods are those methods sent to class objects rather than instances.

@interface AClass
{
}

+(int) a;
+(void) setA: (int) newValue;

@end

// A.m

static int aStorage = 0;

@implementation AClass

+(int) a
{
    return aStorage;
}
+(void) setA: (int) newValue
{
    aStorage = newValue;
}

@end 

// To use:

    int something = [AClass a];
    [AClass setA: something * 2];

// Or dot syntax if you prefer

   AClass.a = AClass.a * 2;

---

First, declaring a static int in your implementation file doesn't magically make it a member of class A; your ObjC class A has no member variables.

Second, ab->a isn't how you would access the member of a class in ObjC. Once you have a member, write a getter for a, and use a method call to access it. (Or if you really want it to be static, don't add a member, and just add a getter that returns the static variable.)