OC学习笔记04--id关键字与构造方法

typedef enum{ColorBlack='b',ColorYellow='y',ColorWhite='w'} Color;#import<Foundation/Foundation.h>@interface Pet : NSObject{@private int _age;double _weight;NSString * _name;}- (id)initWithAge:(int)age andWeight:(double)weight andName:(NSString *)name;-(id)initTest;- (NSString *)toString;@end@implementation Pet// 重写init方法，由于是无参构造方法，无法动态给成员变量赋值- (id)init  {if(self=[super init]) //构造方法中必须调用父类构造方法{_age=1,_weight=1.0,_name=@"pet";}return self;}//自定义构造方法，可以自定义参数，灵活的给成员变量赋值- (id)initWithAge:(int)age andWeight:(double)weight andName:(NSString *)name{if(self=[super init]){_age=age,_weight=weight,_name=name;}return self;}-(id)initTest{if(self=[super init]){//从结果可知，[super class],[self class]都是指向调用者的类对象// 即若由Dog的实例调用，则都指向Dog的类对象，即[Dog class];NSLog(@"super=%d,self=%d,superclass=%d,selfclass=%d,Pet=%d",super,self,[super class],[self class],[Pet class]);}return self;}- (NSString *)toString{return [NSString stringWithFormat:@"name=%@ ,weight=%.2f ,age=%d",_name,_weight,_age]; }@end@interface Dog : Pet{@privateColor _furColor;}- (id)initWithAge:(int)age andWeight:(double)weight andName:(NSString *)name andFurColor:(Color)furColor;@end@implementation Dog- (id)init  {if(self=[super init]) {_furColor=ColorYellow;}return self;}- (id)initWithAge:(int)age andWeight:(double)weight andName:(NSString *)name andFurColor:(Color)furColor{//调用父类的有参构造方法给父类成员赋值if(self=[super initWithAge:age andWeight:weight andName:name]){_furColor=furColor;}return self;}-(id)initTest{if(self=[super initTest]){NSLog(@"Dog=%d",[Dog class]);}return self;}- (NSString *)toString{return [NSString stringWithFormat:@"%@ ,furColor=%c",[super toString],_furColor]; }@endint main(){//id作为万能指针，能指向任意OC对象id *p=[[Dog alloc] init];NSLog(@"this dog is %@",[p toString]);id *p2=[[Dog alloc] initWithAge:4 andWeight:12.2 andName:@"Daisy" andFurColor:ColorWhite];NSLog(@"this dog is %@",[p2 toString]);id *p3=[[Dog alloc] initTest];NSLog(@"p3=%d",p3);return 0;}/*id关键字：typedef struct objc_object { Class isa;} *id;//构造对象相关方法伪代码+ (id)new {return [[self alloc] init];}+ (id)alloc{id obj=(struct objc_object)malloc(父类到子类所有成员变量所占字节数总和);return obj;}- (id)init{//[self class]返回类指针指向当前对象的类对象isa=[self class];return self;}//重写init方法必须调用[super init]来初始化父类中的成员变量  ---类似java无参constructor- (id)init{if(self=[super init]){..初始化操作..}return self;}//自定义构造方法(一般以init开头)  ---类似java有参构造器- (id)initWithName:(NSString *)name{if(self=[super init]){_name=name;}return self;}*/