1. 引用Foundation.h
#import <Foundation/Foundation.h>
2.接口声明:
接口声明代码
//接口定义
@interface Calc:NSObject
{
double _val; //接口变量声明
}
//接口方法声明
-(void) Add:(double) value;
-(void) Sub:(double) value;
-(void) Clear;
-(void) SetVal:(double) value;
-(double) GetVal;
@end
3.接口实现
接口实现格式