oc--Inheritance of iOS development

Three main features of object-oriented

1) Encapsulation (set method and get method, Master)

2) Inheritance (Mastery)

3) Polymorphism (understanding concept can be)

(a) Inheritance (a syntax): is used between classes and classes, representing the relationship between (two) classes.

1. Application of Inheritance

You want to get all the member variables and methods of a class, and what you want to achieve is inherited.

1> when two classes have the same properties and methods, you can extract the same things into a parent class

2> when Class A fully owns some of the properties and methods in class B, consider letting class B inherit class a

Benefits of inheritance:

1> extract Duplicate code, increase code reuse rate

2> establishes a relationship between classes

3> subclasses can have all member variables and methods in the parent class

Disadvantages of inheritance:

Strong coupling of code (that is, class-to-class relationships)

> Note points: basically, the root class of all classes is NSObject

2.

key points of succession:

1) When invoking a method, first detects whether the subclass implements this method, and if the subclass is not implemented, it invokes the implementation of the parent class

2) Rewrite: Subclasses implement methods declared in the parent class

3) A member variable declared inside a subclass cannot have the same name as a member variable declared inside a parent class

code example:

/* * /* 1. Rewrite: Subclasses re-implements a method in the parent class, overwriting the previous practice of the parent Class 2. Note that the 1> parent class must be declared before the child class 2> Subclasses cannot have the same member variable as the parent class 3> call a method, take precedence in the current class to find, if not found, go to the  parent class * *#import <foundation/ foundation.h>@interface person:nsobject     //   Colon represents an inheritance relationship followed by the parent class @end 

(ii) Super

the role of super

1) Call a method in the parent class directly.

2) Super is in the object method, then the parent class's object method is called.

Super is in a class method, then the class method of the parent class is called.

3) Usage Scenarios: Subclasses override the parent class's methods to preserve some behavior of the parent class.

Thought: For some of the same attributes, a common class is generally extracted.

oc--Inheritance of iOS development