先来几段代码，Dog类的.h .m文件 和main.m dog.h #import Foundation/Foundation.h@interface Dog : NSObject{ int _ID; NSString *_name; int _age; float _price;}//凡是用initXXX开头的都是构造函数//init方法实际上没有什么特别的，只是遵循命名约定的普

先来几段代码，Dog类的.h .m文件 和main.m

dog.h

#import 

@interface Dog : NSObject
{
 int _ID;
 NSString *_name;
 int _age;
 float _price;
}
//凡是用initXXX开头的都是构造函数
//init方法实际上没有什么特别的，只是遵循命名约定的普通方法
-(id)init;
-(id)initWithID:(int)newID;
-(id)initWithID:(int)newID andAge:(int)newAge;
-(id)initWithID:(int)newID andAge:(int)newAge andPrice:(int)newPrice;
@property int ID;
@property NSString *name;
@property int age;
@property float price;
@end

#import "Dog.h"

@implementation Dog
-(id)init
{
 return [self initWithID:1001];

}
-(id)initWithID:(int)newID
{
 return [self initWithID:newID andAge:20];
}
-(id)initWithID:(int)newID andAge:(int)newAge
{
 return [self initWithID:newID andAge:newAge andPrice:80.0];
}
-(id)initWithID:(int)newID andAge:(int)newAge andPrice:(int)newPrice
{
 self=[super init];
 if(self){
 _ID=newID;
 _age=newAge;
 _price=newPrice;
 }
 return self;
}

@synthesize ID=_ID;
@synthesize name=_name;
@synthesize age=_age;
@synthesize price=_price;

@end

#import 
#import "Dog.h"
#import "NSString+ReverseString.h"
#import "Person.h"

int main(int argc, const char * argv[])
{

 @autoreleasepool {
 Dog *dog1=[[Dog alloc ] init];
 dog1.name=@"syj";
 NSLog(@"%@",[dog1 name]);
 [dog1 setName:@"ldusyj"];
 NSLog(@"%@",dog1.name);
 }
 return 0;
}

先看一下：

@property

@property int age;

等同于 -setAge:(int)newAge;

-(void)age;

@synthesize

@synthesize age=_age;

等同于： -(void)setAge:(int)newAge{

age=newAge;

}

-(int)age{

return age;

}

1.

dog1.name=@"syj";

等同

[dog1 setName:@"syj"];

NSLog(@"%@",dog1.name);

NSLog(@"%@",[dog1 name]);

注意：

-(void)setAge:(int)newAge 
{ 
 NSLog(@"调用了setAge方法：%i",newAge); 
 self.age = newAge; 
}

不能在setAge:方法中使用self.age = newAge，相当于在setAge:方法中调用[self setAge:newAge ]， 出现死循环

-(int)age 
{ 
 NSLog(@"调用了age方法：%i",_age); 
 return self.age; 
}