メソッド定義

#import 

@interface Calculator : NSObject

//      ‘-’     
- (double) pi;

//       ':'  
- (int) square:(int)num;

//':'         
- (int) sumWithNum1:(int)num1 andNum2:(int)num2;//            

//    '+'    （Java     ）
//            
//         
+ (double) pi;
@end

@implementation Calculator

- (double) pi {
    return 3.14;
}

+ (double) pi {
    return 3.14159;
}

- (int) square:(int)num {
    return num * num;
}

//            
- (int) sumWithNum1:(int)num1 andNum2:(int)num2 {
    return num1 + num2;
}

@end

int main() {
    Calculator *calculator = [Calculator new];
    NSLog(@"%f", [calculator pi]);
    NSLog(@"%i", [calculator square:10]);
    NSLog(@"%i", [calculator sumWithNum1:10 andNum2:10]);
}