Objective-C sample.

main.m

#import <Foundation/Foundation.h>
#import "MyTestClass.h"

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

    @autoreleasepool {
        
        // insert code here...
        NSLog(@"Hello, World!");
        NSLog(@"こんにちはー！！");
        
//        MyTestClass *obj = [MyTestClass alloc];
//        obj = [obj init];
        MyTestClass *obj = [[MyTestClass alloc] init];
        
        [obj setMessage:@"Hello, and GoodBye."];
        [obj printMessage];
        
    }
    return 0;
}