macOS Programmatically creating GUI's in Cocoa?

Not too difficult. In general you can create a new control by calling alloc/initWithFrame:. Then simply call addSubview: on the view you want to add it to. Of course you may well need to do some more setup (set the label on a button for example), but that's the general idea...

If you know basic programming, then all you need is the GUI item's class. Go to it's class and go through the methods that you need to set various attributes, (there are quite a few even for just a button) such as label, size, location, style, color, etc.. I've done it a few times, it gets easy after a while.

And don't forget what robbie said too. Super classes are important as well.

Take a look at the GNUStep tutorials. They do a pretty good job at basic interface building through the API.

Create NSWindow programatically in Cocoa

I hope this helps.

In file main.m:

int main(int argc, char *argv[])
{
WindowController *windowController = [ [ WindowController alloc ] init ];
return NSApplicationMain(argc, (const char **) argv);
}

In file WindowController.mm:

@implementation WindowController

- (id) init
{
self = [ super init ];
if( !self )
return nil;

[ NSBundle loadNibNamed: @"MainMenu" owner: self ];
return self;
}

- (void) awakeFromNib
{
NSRect windowRect = NSMakeRect( 200.0, 200.0, 400.0, 300.0 );

NSWindow *window = [ [ NSWindow alloc ] initWithContentRect:windowRect styleMask NSResizableWindowMask | NSClosableWindowMask | NSTitledWindowMask) backing:NSBackingStoreBuffered defer:NO];

NSButton *button = [ [ NSButton alloc ] initWithFrame: NSMakeRect( 300.0, 20.0, 80.0, 50.0 ) ];

[ button setBezelStyle:NSRoundedBezelStyle];
[ button setTitle: @"Click" ];
[ [ window contentView ] addSubview: button ];
[window makeKeyAndOrderFront:nil];
}

- (void)dealloc
{
[ super dealloc ];
}

@end