Question

I know that we can easily use the objects declare in our appDelegate class by doing this

myAppDelegate *alpha= (myAppDelegate *)[[UIApplication sharedApplication]delegate];

hence from above we can use the alpha object to fetch the value of other objects in myAppDelegate class.

but suppose if I have a Class A and i have declared a NSString *hello in its .h and synthesize it in .m file.

Now in Class B I create an object of class A i.e

A *classA = [[A alloc]init];
A.hello = [NSString stringWithFormat:@"Kawa banga"];
[classA release];

Now in Class C I create an object of Class A again

 A *classA = [[A alloc] init];
NSLog(@"%@",classA.hello);

It gives me null.

How can I get the value of my hello object in different class.

Answer 1

When you declare hello as a property of class A, it’s an instance variable. That means it’s separate for each instance of A you create (with alloc & init).

It looks like you might want to share just 1 instance of A. An easy way of doing this is to add it as a property of your myAppDelegate class. (By the way, class names in Cocoa are usually begin with upper-case letter to distinguish them for variable names)

Once you’ve done that, you’ll be able to access it with:

myAppDelegate *alpha = (myAppDelegate *)[[UIApplication sharedApplication]delegate];
myAppDelegate.classA.hello = @"hello, world";