Property include getter and setter;
you can get property like this:
Object.someProperty;
or
[Object someProperty];
Inheritance
overriding methods
when you override a method, you can only change its implementation.
Youcannot change how it is declared; the method's name ,return type ,
and argument types must stay the same;
Inheritance hierarchy
NSObject has many methods but only one instance variable: the isa pointer.
Every object's isa pointer points at the class that created it. (Get it ? When
you have a BNRPerson instance , that object "is a" BNRPerson.
When you have an NSString instance, that object "is a [n]" NSString.)
The first implementation that is found is t
he one that gets executed..
description and %@
The token %@ use to get an object to describe itself .The %@ token sends a descroption
message to the object pointed to by the corresponding variable.
NSObeject has many methods but only one instance variable: the isa pointer.Every object's isa pointer points at the class that created it.(Get it ? When you have a BNRPerson instance , that object "is a" BNRPerson. When you have an NSString instance , that object "is a[n]" NSString.)
The descroption method returns a string that is a useful description of an instance of the class . It is an NSObject method,so evety object implements it.The default NSObject implementation returns the object's address in memory as string.
