3. Objective-C for encapsulation inheritance and Polymorphism

Three Characteristics of object-oriented encapsulation, inheritance, and Polymorphism

Encapsulation: Hiding internal implementations and stabilizing external interfaces.

Encapsulation is to define the class definition property definition method.

Property encapsulates the setter get Method

@ Property (nonatomic, retain) nsstring * Name, * sex;

Class encapsulates instance variables and Methods

. H file

# Import <Foundation/Foundation. h>

@ Interface person: nsobject

{

Nsstring * _ name;

Nsstring * _ sex;

Int _ age;

}

@ Property (nonatomic, retain) nsstring * Name, * sex;

@ Property (nonatomic, assign) int age;

-(ID) initwithname :( nsstring *) Name sex :( nsstring *) sex age :( INT) age;

-(Person *) work;

@ End

. M file

# Import "person. H"

@ Implementation person

@ Synthesize name = _ name, sex = _ sex, age = _ age;

-(ID) initwithname :( nsstring *) Name sex :( nsstring *) sex age :( INT) Age

{

Self = [Super init];

If (Self ){

Self. Name = Name;

Self. Sex = sex;

Self. Age = age;

}

Return self;

}

-(Person *) Work

{

Nslog (@ "% @ working", self. Name );

Return 0;

}

@ End

Inheritance: Child classes can directly reuse members in the parent class. Child classes inherit the declaration of all methods of the parent class and implement non-private instance variables and protocols.

Inheritance is to declare in. H that inheritance has a single and pass-through inheritance, that is, the common part of code optimization is handed over to the parent class.

# Import "person. H"

@ Interface worker: person // subclass: parent class

@ End

# Import "person. H"

@ Interface King: person

@ End

Inheritance in OC: Single-core (one sub-class can only have one super class)

Passed (a-> B-> C A-> C)

Polymorphism: different objects have different responses to the same message. sub-classes can override the parent class method.

Polymorphism means that the parameter or returned value of the method can be input or returned as a parent type.

Worker * worker = [[Worker alloc] init];

Worker. Name = @ "worker ";

[Worker work];

King * King = [[King alloc] init];

King. Name = @ "King ";

[King work];