#import <Foundation/Foundation.h>@interface ClassVirable : NSObject{    NSInteger year;//保护树形}@property int age;//不用在实现文件中写@synthesize age就会有setAge:和age方法了-(void)set:(NSInteger)i;@end

#import "ClassVirable.h"@implementation ClassVirable///Property implementation must have its declaration in interface ‘ClassVirable‘//@synthesize year;-(void)set:(NSInteger)i{    self.age = i;    year = i;}@end

#import <Foundation/Foundation.h>#import "ClassVirable.h"int main(int argc, const char * argv[]){    @autoreleasepool {        ClassVirable *c = [[ClassVirable alloc]init];        [c set:2];        [c setAge:20];        NSLog(@"%i",[c age]);        NSLog(@"%i",c.age);        //Instance variable ‘year‘ is protected//        NSLog(@"%ld",(long)c->year);    }    return 0;}