How to pass values by reference in objective C (iphone)

Question

Pass-by-reference in Objective-C is the same as it is in C.

The equivalent to the following C# code:

void nullThisObject(ref MyClass foo)
{
    foo = null;
}

MyClass bar = new MyClass();
this.nullThisObject(ref bar);
assert(bar == null);

is

- (void)nilThisObject:(MyClass**)foo
{
    [*foo release];
    *foo = nil;
}

MyClass* bar = [[MyClass alloc] init];
[self nilThisObject:&bar];
NSAssert(bar == nil);

and

- (void)zeroThisNumber:(int*)num
{
    *num = 0;
}

int myNum;
[self zeroThisNumber:&myNum];
NSAssert(myNum == 0);

If you use Objective C++, which you can do by naming your file with extension .mm, or telling Xcode to compile all source as Objective C++, then you can pass references in the same way you do with C++, eg:

- (OSStatus) fileFileInfo: (FileInfo&)fi;

There is no passing by reference (in C++ sense) in Objective C. You can pass your objects by pointer, and for primitive types by value.

Example:

void func(NSString* string)
{
  ...
}

void func(NSInteger myint)
{
 ...
}

..
NSString* str = @"whatever";
NSInteger num = 5;

func(str);
func(num); 

Try this way :

    -(void)secondFunc:(NSInteger*)i
    {
      *j=20;
     //From here u can change i value as well
     //now i and j value is same (i.e i=j=20)
    }
    -(void) firstFunc
    {
       NSInteger i=5;
      [self secondFunc :&i];
     //i value is 20
    }

Hope it helps!!