Calling a routine from another module

G'day All,

So many painful little problems.

if my module looks like this:

#import "controller.h"
@implementation controller
-(void)PrintHello
{
    NSLog(@"I got this far");
    [txtFloatIn setStringValue:[NSString stringWithString:@"Hello"]];
}

-(IBAction)PrintFloat:(id)sender
{
    float myVar;
    
    myVar = [txtFloatIn floatValue];

    [txtStringOut setStringValue:[NSString stringWithFormat:@"The number is %f",myVar]];
    
    //[self PrintHello];
    
}

@end

What do I put in the appDelegate to call PrintHello on start up.

I thought [controller PrintHello] would do it since [self PrintHello] works from within the controller module.

BTW the appDelegate.m looks like this:

#import "Float_to_StrAppDelegate.h"
#import "controller.h"
@implementation Float_to_StrAppDelegate

@synthesize window;

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
    // Insert code here to initialize your application
    NSLog(@"The delegate ran");
    [controller PrintHello];
}

@end

When I run this app the NSLog reports when the appDelegate runs but then I get an error:

+[controller PrintHello]: unrecognized selector sent to class 0x100002160

All help gratefully accepted.  I've been trawling the net for an hour trying solve this.

Cheers,
A.