iOS 应用开发（二）OC 面向对象之类与对象

（一）概述

OC 对象的本质就是结构体。类的声明要放前面，类的实现可以放后面；同时要注意方法和函数(OC完全兼容C)的区别：方法的实现只能写在@implementation里面，而函数可以写在任意位置（归文件所有）且它的调用不依赖于对象。

ios-oop.png

（二）类的声明和实现

#import <Foundation/Foundation.h>

// 类的声明
// : NSObject 目的是让 Car 具备创建对象能力
@interface Car : NSObject {
    @public// @public 让外部指针允许访问对象内部成员
    int wheels;// 默认为0（不允许在这初始化）
    double speed;
}
// 方法声明（必须以减号 - 开头）
// 注意：任何数据类型必须加()，且仅加在数据类型上
- (void)driver;

@end

// 类的实现（实现声明的方法）
@implementation Car
- (void)driver {
    NSLog(@"%d个轮子，速度%fkm/h的车子正在驾驶中...",wheels,speed);
}

@end

// 函数传值
void testValue(int wheels,double speed) {
    wheels = 10;
    speed = 200.0;
}

// 函数传地址
void testPoint(Car *car) {
    car->wheels = 10;
    car->speed = 200.0;
}

// [对象 方法]
int main(int argc, const char * argv[]) {
    // [Car new] 创建一个 Car 对象并返回该对象本身（地址）
    // 指针 p 指向 Car 类型的对象
    Car *p = [Car new];
    // 将指针 p 赋值给指针 p2
    Car *p2 = p;
    p->wheels = 4;
    p->speed = 120.0;
    NSLog(@"wheels=%d,speed=%f,%p,%p",p2->wheels,p2->speed,p2,p);
    [p2 driver];// 调用run方法

    // ============= 函数 ============//
    // 传值，属性不变
    testValue(p->wheels,p->speed);
    [p driver];
    
    // 传地址，属性改变
    testPoint(p);
    [p driver];
    
    return 0;
}

（三）枚举和结构体

#import <Foundation/Foundation.h>

typedef enum {
    SexMan,
    SexWoman
} Sex;

typedef struct {
    int year;
    int month;
    int day;
} Date;

typedef enum {
    ColorRed,
    ColorGreen,
    ColorBlue
} Color;

// Dog
@interface Dog: NSObject {
    @public
    double weight;
    Color color;
    char *name;
}
- (void)eat;
- (void)run;

@end

@implementation Dog
- (void)eat {
    weight++;
    NSLog(@"Dog eat...weight=%f",weight);
}

- (void)run {
    weight--;
    NSLog(@"Dog run...weight=%f",weight);
}

@end

// Person
@interface Person : NSObject{
    @public
    Sex sex;
    Date birthday;
    double weight;
    Color favorColor;
    char *name;
    Dog *dog;// 使用指针
}
- (void)eat;
- (void)run;
- (void)print;
- (void)walkDog;
- (void)feedDog;

@end

@implementation Person
- (void)eat {
    weight++;
    NSLog(@"Person eat...weight=%f",weight);
}

- (void)run {
    weight--;
    NSLog(@"Person run...weight=%f",weight);
}

- (void)print {
    NSLog(@"sex=%d,birthday=%d-%d-%d,weight=%f,favorColor=%d, name=%s,Dog(weight=%f,color=%d,name=%s)",sex,birthday.year,birthday.month,birthday.day,weight,favorColor,name,dog->weight,dog->color,dog->name);
}

- (void)walkDog {
    [dog run];
}

- (void)feedDog {
    [dog eat];
}

@end

int main() {
    Person *s = [Person new];
    s->weight = 100.0;
    s->sex = SexWoman;
    
    // Date 第一种写法(推荐)：
    Date d = {2022,12,14};
    s->birthday = d;
    // Date 第二种写法：
    s->birthday.year = 2022;
    s->birthday.month = 12;
    s->birthday.day = 14;
    
    s->favorColor = ColorRed;
    s->name = "CloudKK";
    
    // Dog
    Dog *dog = [Dog new];
    dog->weight = 30.0;
    dog->color = ColorGreen;
    dog->name = "XiaoHei";
    s->dog = dog;

    [s eat];
    [s run];
    [s walkDog];
    [s feedDog];
    // sex=1,birthday=2022-12-14,weight=100.000000,favorColor=0, name=CloudKK,Dog(weight=30.000000,color=1,name=XiaoHei)
    [s print];
   
    return 0;
}

（四）普通类型参数

在OC方法中，一个参数对应一个冒号。

#import <Foundation/Foundation.h>

@interface Calculator : NSObject
- (double)pi;
// 在OC方法中，一个参数对应一个冒号
- (int)square : (int)num;
// 方法名 sum:andNum2: 注意这里的冒号也是它的一部分
// 其中 andNum2 为描述符（可不写）
- (int)sum : (int)num1 andNum2 : (int)num2;
- (int)sumSquare : (int)num1 : (int)num2;

@end

@implementation Calculator
- (double)pi {
    return 3.14;
}

- (int)square : (int)num {
    return num * num;
}

- (int)sum : (int)num1 andNum2 : (int)num2 {
    return num1 + num2;
}

- (int)sumSquare : (int)num1 : (int)num2 {
    return num1 * num1 + num2 * num2;
}

@end

int main() {
    Calculator *c = [Calculator new];
    double pi = [c pi];
    NSLog(@"pi=%f",pi);
    
    int square = [c square:9];
    NSLog(@"square=%d",square);
    
    int sum = [c sum:9 andNum2:10];
    NSLog(@"sum=%d",sum);
    
    int sumSquare = [c sumSquare:9: 10];
    NSLog(@"sumSquare=%d",sumSquare);
    return 0;
}

（五）指针类型参数

#import <Foundation/Foundation.h>

@interface Car : NSObject {
    @public
    int speed;
}
// 传指针类型参数
- (int)compareSpeedWithOther : (Car *)other;

@end

@implementation Car
- (int)compareSpeedWithOther : (Car *)other {
    return speed - other->speed;
}

@end

int main() {
    Car *car1 = [Car new];
    car1->speed = 100;
    
    Car *car2 = [Car new];
    car2->speed = 120;
    
    int result = [car1 compareSpeedWithOther: car2];
    NSLog(@"result=%d",result);
    
    // 匿名对象（不推荐）
    // [Car new]->speed = 100;
    // [[Car new] run];
    
    return 0;
}