1.拆分接口和实现
类的定义中，代码很自然的被拆分为接口和实现两个部分，所有类的代码通常分别放在两个文件中
- 存放接口部分的代码：类的@interface指令，公共的struct定义，enum常量，#defines和extern全局变量等，将其放在头文件中，头文件名称与类名相同，只是用.h做后缀
- 存放实现部分的代码：类的@implementation指令，全局变量的定义，私有struct等，将其放在实现文件中，实现文件与类名相同，只是用.m做后缀
图片示例
New F[图片上传中...(屏幕快照 2018-10-06 09.23.12.png-684e52-1538843150512-0)]
ile
Cocoa Class
命名
2.拆分Car程序
简单的拆分
//main.m 文件
#import <Foundation/Foundation.h>
#import "Engine.h"
#import "Tire.h"
//Car类
@interface Car : NSObject{
Engine *engine;
Tire *tires[4];
}
-(void)print;
@end
@implementation Car
//初始化实例变量的init方法
-(id)init{
if (self = [super init]) {
engine = [Engine new];
tires[0] = [Tire new];
tires[1] = [Tire new];
tires[2] = [Tire new];
tires[3] = [Tire new];
}
return self;
}
//通过NSLog()输出实例变量，记住%@只是调用每个对象的description
-(void)print{
NSLog(@"%@",engine);
NSLog(@"%@",tires[0]);
NSLog(@"%@",tires[1]);
NSLog(@"%@",tires[2]);
NSLog(@"%@",tires[3]);
}
@end//Car
int main(int argc, const char * argv[]) {
Car *car;
car = [Car new];
[car print];
return 0;
}
//类.h文件
//Engine类
#import <Foundation/Foundation.h>
@interface Engine : NSObject
@end
//Tire类
#import <Foundation/Foundation.h>
@interface Tire : NSObject
@end
//类.m文件
//Engine类
#import "Engine.h"
@implementation Engine
- (NSString *) description{
return (@"I am a engine");
}
@end
//Tire类
#import "Tire.h"
@implementation Tire
- (NSString *) description{
return (@"I am a tire");
}
@end
//运行结果
2018-10-06 09:34:11.409383-0700 Car-拆分-简单[627:15686] I am a engine
2018-10-06 09:34:11.409995-0700 Car-拆分-简单[627:15686] I am a tire
2018-10-06 09:34:11.410040-0700 Car-拆分-简单[627:15686] I am a tire
2018-10-06 09:34:11.410064-0700 Car-拆分-简单[627:15686] I am a tire
2018-10-06 09:34:11.410175-0700 Car-拆分-简单[627:15686] I am a tire
Program ended with exit code: 0
可能的错误及解决方法
出现clang: error: linker command failed with exit code 1 (use -v to see invocation)错误的解决方法
3.使用跨文件依赖关系
依赖关系是两个实体之间的一种关系.依赖关系可以存在于两个类之间，也可以存在于两个或多个文件之间
复杂的拆分
文件
//main.m 文件
#import <Foundation/Foundation.h>
#import "Engine.h"
#import "Tire.h"
#import "Car.h"
int main(int argc, const char * argv[]) {
Car *car;
car = [Car new];
[car print];
return 0;
}
//类.h文件
//Engine类
#import <Foundation/Foundation.h>
@interface Engine : NSObject
@end
//Tire类
#import <Foundation/Foundation.h>
@interface Tire : NSObject
@end
//Car类
#import <Foundation/Foundation.h>
#import "Engine.h"
#import "Tire.h"
@interface Car : NSObject{
Engine *engine;
Tire *tires[4];
}
-(void)print;
@end
//类.m文件
//Engine类
#import "Engine.h"
@implementation Engine
- (NSString *) description{
return (@"I am a engine");
}
@end
//Tire类
#import "Tire.h"
@implementation Tire
- (NSString *) description{
return (@"I am a tire");
}
@end
//Car类
#import "Car.h"
@implementation Car
//初始化实例变量的init方法
-(id)init{
if (self = [super init]) {
engine = [Engine new];
tires[0] = [Tire new];
tires[1] = [Tire new];
tires[2] = [Tire new];
tires[3] = [Tire new];
}
return self;
}
//通过NSLog()输出实例变量，记住%@只是调用每个对象的description
-(void)print{
NSLog(@"%@",engine);
NSLog(@"%@",tires[0]);
NSLog(@"%@",tires[1]);
NSLog(@"%@",tires[2]);
NSLog(@"%@",tires[3]);
}
@end
//运行结果
2018-10-06 09:55:42.394801-0700 Car-拆分-复杂[838:23762] I am a engine
2018-10-06 09:55:42.395053-0700 Car-拆分-复杂[838:23762] I am a tire
2018-10-06 09:55:42.395071-0700 Car-拆分-复杂[838:23762] I am a tire
2018-10-06 09:55:42.395079-0700 Car-拆分-复杂[838:23762] I am a tire
2018-10-06 09:55:42.395085-0700 Car-拆分-复杂[838:23762] I am a tire
Program ended with exit code: 0
4.@class
在学习过程中，我们认识了文件的依赖关系，在这种关系中，头文件或源文件需要使用另一个头文件的信息.文件导入过于混乱会延长编译时间，也会导致不必要的重复编译，而巧妙地使用@class指令告诉编译器“相信我，你最终肯定会了解这个名称的类”，可以减少必须导入的头文件的数量，从而可以缩短编译时间
示例：
//Car类的接口
#import <Foundation/Foundation.h>
@class Tire;
@class Engine;
@interface Car : NSObject{
Engine *engine;
Tire *tires[4];
}
-(void)print;
@end
//这样就可以告诉编译器处理Car类的@interface部分所需要的全部信息了
