CODEWITHSUNDEEP
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Abdul Rahman
Abdul Rahman

Reputation: 986

public private and protected in objective-c

Hi I am trying to learn Opps concept in Objective C but I know PHP so I took a program in which for public, private and protected mentioned bellow.

<?php


//Public properties and method can be inherited and can be accessed outside the class.
//private properties and method can not be inherited and can not be accessed outside the class.
//protected properties and method can be inherited but can not be accessed outside the class.

class one
{
    var $a=20;
    private $b=30;
    protected $c=40;
}

class two extends one
{

    function disp()
    {
        print $this->c;
        echo "<br>";
    }
}

$obj2=new two;
$obj2->disp();  //Inheritance
echo"<br>";

$obj1=new one;
print $obj1->c; //Outside the class

?>

So this I am trying to convert in Objective c code mentioned bellow.

#import <Foundation/Foundation.h>
@interface one : NSObject
{
@private int a;
@public int b;
@protected int c;
}
@property int a;
@property int b;
@property int c;

@end
@implementation one
@synthesize a,b,c;
int a=10;
int b=20;
int c=30;
@end

@interface two : one

-(void)setlocation;

@end

@implementation two

-(void)setlocation;
{
   // NSLog(@"%d",a);
    NSLog(@"%d",b);
   // NSLog(@"%d",c);
}

@end
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        // insert code here...
        two *newtwo;
        newtwo =[[two alloc]init];
        //calling function
        [newtwo setlocation];    
    }
    return 0;
}

When I run the above code I am getting

2015-11-03 23:20:16.877 Access Specifier[3562:303] 0

Can some one resolve my problem.

Upvotes: 1

Views: 2642

Answers (1)

Joseph Quigley
Joseph Quigley

Reputation: 346

This type of question has been asked before and there's a good explanation in the accepted answer for Private ivar in @interface or @implementation

In general I would recommend you avoid instance variables and use @property instead. Properties have the benefit of read-only/write controls, and free synthesized setters and getters (which if you're learning OOP concepts is a critical concept you should employ).

Properties are declared in the @interface part of an Obj-C file. For access control (according to the link) you have no public/private/protected keywords. All Obj-C methods (and by extension, properties) are public if they're defined in the .h file. If you want them "private" you define them in the the .m file using a class category:

//MyClass.m
@interface MyClass ()
@property(nonatomic, retain) NSString* myString;
@end

@implementation MyClass
@end

Upvotes: 1

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