Encapsulation, inheritance, polymorphism in objective-c

Benefits of Encapsulation:

1. Filter for unreasonable values
2. The assignment process inside the Shield
3. Let the outside world not pay attention to the internal details

Benefits of Inheritance:

1. Do not change the original model based on the method of extension charge

2. Establish a connection between classes and classes

3. The public code was extracted

4. Cons: Strong coupling (when a parent class is removed, the subclass will no longer be used)

Points of note for inheritance:

1. Subclasses and parent classes cannot have the same member variable
2. Subclasses can override methods of the parent class
3. Access procedure for subclass methods and properties: If the subclass does not have access to the parent class's

Inheritance and Composition:

1 @interfaceScore:nsobject2 {3         int_cscore;4         int_ocscore; 5 }6 @end7 8 @implementationscore9 @endTen  One @interfaceStudent:nsobject A { -Score *_socre;//There's a combination here, because you can't say that grades are a student . -        int_age;  the } - @end -  - @implementationStudent + @end

Combinations and inheritance can be understood as follows:

• Inheritance is xxx is xxx
• combination is xxx own xxx

polymorphism is simply saying: The parent pointer points to the subclass object

Benefits of Polymorphism:

• Receive parameters with parent class, save code

#import<Foundation/Foundation.h>@interfaceAnimal:nsobject@end@implementationAnimal- (void) eat{NSLog (@"Animal----Eat food");}@end@interfaceDog:animal@end@implementationDog- (void) eat{NSLog (@"Dog----Eat food");}@end@interfaceCat:animal@end@implementationCat- (void) eat{NSLog (@"Cat----Eat food");}@end//the parent class type used in the parameter can pass in the child class, the parent class objectvoidFeed (Animal *a) {[A eat];}//This function embodies the benefits of polymorphism, saving codeintMain () {Animal*AA =[[Animal alloc] init];        Feed (AA); Dog*DD =[[Dog alloc] init];        Feed (DD); Cat*CC =[[Cat alloc] init]; Feed (cc);}

Limitations of polymorphism:

• A variable of the parent class type cannot directly invoke a specific method of the subclass (cast is used)

// Forced Conversions Person *p = [[Student alloc] init]; // If the study is a student-specific method, if you want to call a forced conversion // OC is weak syntax if [P study] can also (is dynamic bound), but because the compiler will appear warning, so do not write with a cast to make it more reasonable Student *s = (Student *) p;[ s study];

• Dynamic binding: Determines the method of dynamic invocation at run time based on the type of object

Encapsulation, inheritance, polymorphism in objective-c