Iphone开发(3) 一个使用组合的简单例子

#import <Foundation/Foundation.h>//导入文件有两种方式：#import" "和#import<>，第一种代表引入你自己的文件，第二种代表引入系统的文件//文件的引用：在接口文件中，使用@class；在实现文件中，使用#import// --------------------------------------------------@interface Tire : NSObject@end@implementation Tire- (NSString *) description//此方法类似于Java里面的toString{    return (@"I am a tire. I last a while");}@end// --------------------------------------------------@interface Engine : NSObject@end@implementation Engine- (NSString *) description{return (@"I am an engine.  Vrooom!");} @end// --------------------------------------------------@interface Car : NSObject{Engine *engine;Tire *tires[4];}- (void) print;@end@implementation Car- (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);}- (void) print{NSLog (@"%@", engine);NSLog (@"%@", tires[0]);NSLog (@"%@", tires[1]);NSLog (@"%@", tires[2]);NSLog (@"%@", tires[3]);} @end // --------------------------------------------------int main (int argc, const char * argv[]) {Car *car;car = [[Car alloc] init];[car print];return (0);}