数据类型之id类型

id数据类型可以存储任何类型的对象。在概念上类似于Java中的Object类，可以被转换为任何数据类型。在内部处理中，id是一个指向任何一个继承了Object或者NSObject类的对象，在使用时不用加星号。

Student.h

#import <Foundation/Foundation.h>

@interface Student : NSObject
{
    int sid; //学号
    NSString *name; //姓名
}

@property int sid;
@property (nonatomic,retain)NSString *name;

-(void)print;   //声明一个名为print的实例方法
-(void)setSid:(int)sid andName:(NSString*)name;

@end

Student.m

#import "Student.h"

@implementation Student
@synthesize sid,name;

-(void)print
{
    NSLog(@"My number is %i,and My name is %@",sid,name);
}
-(void)setSid:(int)sid1 andName:(NSString*)name1
{
    self.sid=sid1;
    self.name=name1;
}

@end

Member.h

#import <Foundation/Foundation.h>

@interface Member : NSObject
{
    int age;
    NSString *name;
}

@property(nonatomic,retain)NSString *name;
@property int age;

-(void)print;
-(void)setName:(NSString *)name1 andAge:(int)age1;

@end

Member.m

#import "Member.h"

@implementation Member
@synthesize age,name;

-(void)print{
    NSLog(@"Myname is %@,Myage is %i",name,age);
}

-(void)setName:(NSString *)name1 andAge:(int)age1{

    self.age=age1;
    self.name=name1;
}

@end

main.m

#import <UIKit/UIKit.h>

#import "AppDelegate.h"
#import "Member.h"
#import "Student.h"
 

int main(int argc, char * argv[])
{
    @autoreleasepool {
        NSLog(@"My First App is Run!");        //为什么加了这句以后下面的print就打不出来了？
        Member *member1=[[Member alloc]init];
        [member1 setName:@"zhangsan" andAge:24];
        id data;    //定义了一个id类型的变量data
        data=member1;
        [data print];
        
        Student *student1=[[Student alloc]init];
        [student1 setSid:9527 andName:@"huaan"];
        data=student1;
        [data print];             
    }   
    return 0;
}