问如何在Xcode中用一个简单的按钮调用另一个类中的方法

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//  ViewController.h


#import <UIKit/UIKit.h>
#import <Foundation/Foundation.h>
#import "PrintHello.h"

@interface ViewController : UIViewController <NSObject>{

PrintHello *printMessage;
}

@property (nonatomic, retain) PrintHello *printMessage;
@end

//  ViewController.m
#import "ViewController.h"
@interface ViewController ()
@end

@implementation ViewController
@synthesize printMessage;


- (void)viewDidLoad{
[super viewDidLoad];
NSLog(@"ViewDidLoad loaded");
}


- (IBAction)Button01:(id)sender{

self.printMessage = [[PrintHello alloc] init]; // EDIT: THIS LINE WAS MISSING NOW IT WORKS

[self.printMessage Print];
NSLog(@"Button01 Pressed");    
}
@end

//  PrintHello.h
#import <Foundation/Foundation.h>

@interface PrintHello : NSObject
-(void) Print;
@end

#import "PrintHello.h"
@implementation PrintHello 

-(void)Print{ NSLog(@"Printed");}

@end