Question

I am having trouble to understand the concept of private instance variables in Objective-C:

Let’s assume I have a class:

@interface Dog : NSObject

and two declared selectors

- (void)setSomeString:(NSString *)_someString;
- (NSString *)someString;

in the Dog.m implementation file I declare a private instance variable:

@interface Dog()
{
  NSString *someString;
}

in the main method of the program I create a new dog object:

Dog *myDog = [[Dog alloc] init];

Why is it possible to do something like this out of the main method?

myDog.someString = @"Yoda";

I would expect the someString-variable to be private and only accessible by its setter

[myDog setSomeString:@"Yoda"];

Answer 1

When you use dot-syntax you are actually calling method setSomeString, the difference is just in syntax, not in meaning 🙂

Check Apple documentation about sending a message to an object