Property: What's the difference between strong and copy. Blogpost: http://stackenblochen.blogsport.eu/2014/02/25/property-strong-and-copy/

strong-copy.m

//
//  main.m
//  strong_retain_copy
//
//  Created by Christopher Loessl on 25/02/14.
//  Copyright (c) 2014 Christopher Loessl. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface Person : NSObject

@property (strong, nonatomic) NSString *name;
@property (copy, nonatomic) NSString *nick;

@end

@implementation Person

@end

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

    @autoreleasepool {
        
        Person *per = [[Person alloc] init];
        NSMutableString *aName = [NSMutableString stringWithString:@"Christopher"];
        
        // The pointer "per.name" is changed.
        // "per.name" points at the same location as "someName" afterwards
        per.name = aName;
        
        // This is equal to
        // per.address = [someName copy];
        // Therefore the points are not the same afterwards
        per.nick = aName;
        
        // Changing "someName" to
        [aName setString:@"hashier"];
        
        NSLog(@"per.name   : %@", per.name);
        NSLog(@"per.nick   : %@", per.nick);
        NSLog(@"someName   : %@", aName);
        NSLog(@"\nPointer 1: %p\nPointer 2: %p\nPointer 3: %p", per.name, per.nick, aName);
        
    }
    return 0;
}