Question

i can’t understand how make a variable private in Object-C, in Java i can do it in this way:

public class Counter {
private int cont;

public Counter(){
    cont = 0;
}
public Counter(int v){
    cont = v; }

public void setValue(int v){
    cont = v;
}
public void inc(){
    cont++; }

public int getValue(){
    return cont;
}
}

and then:

public class MyClass extends Counter {

public static void main(String[] args) {

    Counter myC = new Counter();

    System.out.println(myC.getValue());
    //System.out.println(myC.cont); don't work because it's private
}

}

so i can’t access at the variable myC.cont because obviously it’s private, in Object-C i make the same thing but don’t work:

@interface Counter : NSObject {
@private int count;
}

- (id)initWithCount:(int)value;
- (void)setCount:(int)value;
- (void)inc;
-(int)getValueCount;

@end

#import "Counter.h"

@implementation Counter

-(id)init {

count = 0;

return self;
}

-(id)initWithCount:(int)value {

self = [super init];

[self setCount:value];

return self;

}

- (void)setCount:(int)value {

count = value;
}

- (void)inc {

count++;
}

-(int)getValueCount {

return count;
}

@end

and then call it from the main.m:

#import "Counter.h"

int main(int argc, const char * argv[])
{

@autoreleasepool {

    NSLog(@"Hello, World!");
    Counter *myC = [[Counter alloc] init];
    [myC inc];
    [myC inc];
    [myC inc];

    myC.count = 1;
    NSLog(@"%d",myC.getValueCount); //it's 1 instead of 3


}
return 0;
}

i can’t understand i can access at the count variable, how i can make it private like in java?

Answer 1

myC.count is not accessing your variable, its accessing the method you defined -(int)count;. Because myC is a pointer, of type Counter, you access its member variables directly by dereferencing the pointer like so myC->count. This is not advisable however. Obj-C has built in functionality for generating getters and setters with the @property keyword.

But a break point in `-(int)count and watch as that method gets invoked.