继承与派生

继承与派生
1.1继承：也是两个类之间的一种关系
1.2是父类与子类之间的一种关系，需要满足“is a”的条件
1.3子类继承父类之后，将父类中的所有属性和方法直接在子类中复用
1.4派生：在子类中添加自己的属性与方法

1.5super指针指向子类对象中继承过来的父类属性和方法 super指针.png
1.6重写：在子类中对父类继承过来的方法重新定义函数体
1.7隐藏：子类重写父类的方法后，用子类的对象调用该方法时，优先调用子类重写的方法
1.8 private与protected（访问方法）
1.8.1private:作用域仅在所定义的类中（私有的）
1.8.2protected:作用域在所定义类及其子类中（保护的）

TRAnimal.h

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@interface TRAnimal : NSObject
{
    int _a;//保护的作用域在所定义类及其子类中
    @private
    int _b;//作用域仅在所定义的类中
}
@property NSString *name;
@property int age;
-(id)initWithName:(NSString *)name andAge:(int)age;//带参初始化
+(id)animalWithName:(NSString *)name angAge:(int)age;//带参工厂
-(NSString *)eat;
-(NSString *)sleep;
@end

NS_ASSUME_NONNULL_END

TRAnimal.m

#import "TRAnimal.h"

@implementation TRAnimal
-(id)initWithName:(NSString *)name andAge:(int)age
{
    self = [super init];
    if (self)
    {
        self.name = name;
        self.age = age;
    }
    return self;
}
+(id)animalWithName:(NSString *)name angAge:(int)age
{
    TRAnimal *a = [[TRAnimal alloc]initWithName:name andAge:age];
    return a;
}
-(NSString *)eat
{
    return [NSString stringWithFormat:@"动物%@吃",self.name];
}
-(NSString *)sleep
{
    return [NSString stringWithFormat:@"动物%@睡",self.name];
}
-(NSString *)description
{
    return [NSString stringWithFormat:@"名字：%@\n年龄：%d",self.name,self.age];
}
@end

TRDog.h(子类)

@interface TRDog : TRAnimal
-(NSString *)watchHome;
@property int weight;
-(id)initWithName:(NSString *)name andAge:(int)age andWeight:(int)weight;
@end

TRDog.m

@implementation TRDog
-(NSString *)watchHome
{
    return [NSString stringWithFormat:@"狗狗%@正在看家", self.name];
}
-(id)initWithName:(NSString *)name andAge:(int)age andWeight:(int)weight
{
    self = [super initWithName:name andAge:age];
    if(self)
       {
           self.weight = weight;
       }
    return self;
}
-(NSString *)eat
{
    _a = 10;//作用域在所定义类及其子类中（保护的）
    //_b = 20;作用域仅在所定义的类中（私有的）
    NSString *str = [super eat];
    str = [str stringByAppendingFormat:@"\n狗狗%@正在啃骨头",self.name];
    return str;
}

ViewController.m

#import "ViewController.h"
#import "TRDog.h"
#import "TRCat.h"
@interface ViewController ()
@property (weak, nonatomic) IBOutlet UILabel *outputLabel;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    TRDog *  dog = [[TRDog alloc]init];
    dog.name = @"旺财";
    dog.age = 2;
    self.outputLabel.text = [dog eat];
    
    TRCat *cat = [[TRCat alloc] initWithName:@"加菲猫" andAge:1];
    self.outputLabel.text = [cat sleep];
    self.outputLabel.text = [dog watchHome];
    self.outputLabel.text = [cat catchMouse];
    TRDog *dog1 = [[TRDog alloc] initWithName:@"阿黄" andAge:3 andWeight:5];
    self.outputLabel.text = [dog1 eat];
}