Some basics first. With objects, you need to deal with their attributes. Ordinarily, we do instance.attribute. Sometimes we need more control (when we do not know the name of the attribute in advance). For example, instance.attribute would become getattr(instance, attribute_name). Using this model, we can get the attribute by supplying the attribute_name as a string. … Read more
A synthesized ivar is completely invisible to all code that cannot see the @synthesize line (which basically means anything outside of the .m file). It’s not @protected, it’s not @private, it’s simply unknown. With a @private ivar, other code trying to access it will be told that it’s private, but with a synthesized ivar, other … Read more
Lot of good answers, but maybe one more from a self-taught Java programmer as I went through all that by myself with a lot of pain 😉 Think about a Class as something seen from the outside, not as something you see internally. If you look at a Class from the outside, what you see? … Read more
It doesn’t grant you anything extra beyond being concise. If you prefer the more verbose syntax, then by all means, use that. One advantage to using auto props is that it can potentially save you from making a silly coding mistake such as accidentally assigning the wrong private variable to a property. Trust me, I’ve … Read more
Abstraction is a process where you show only “relevant” data and “hide” unnecessary details of an object from the user. Consider your mobile phone, you just need to know what buttons are to be pressed to send a message or make a call, What happens when you press a button, how your messages are sent, … Read more
Encapsulation: hiding data using getters and setters etc. Abstraction: hiding implementation using abstract classes and interfaces etc.
Why don’t I have an error message, when I set ID value in daughter class, the sentence this.id=value is executed, but how can can I access to it from my child class if it is private? When you call a public method on a class, that method can access private members of that class: public … Read more
Access to the book is by no mean necessary. The issues we are dealing here are Dependency and Reuse. In a well-designed software, you try to isolate items from one another so as to reduce Dependencies, because Dependencies are a hurdle to overcome when change is necessary. In a well-designed software, you apply the DRY … Read more
1) why I would want to use properties instead of fields (especially when it appears I am just adding additional code You should always use properties where possible. They abstract direct access to the field (which is created for you if you don’t create one). Even if the property does nothing other than setting a … Read more
Set and Get methods are a pattern of data encapsulation. Instead of accessing class member variables directly, you define get methods to access these variables, and set methods to modify them. By encapsulating them in this manner, you have control over the public interface, should you need to change the inner workings of the class … Read more