Select an image file using a sheet in Cocoa

gistfile1.m

NSArray *allowedImageFileExtensions = [NSArray arrayWithObjects:@"png",@"jpg",@"jpeg",@"gif",@"bmp",nil];

// ...

- (IBAction)displayImagePickerSheet:(id)sender {
	NSOpenPanel *panel = [NSOpenPanel openPanel];
	[panel setAllowedFileTypes:allowedImageFileExtensions];
	[panel setDirectory:NSHomeDirectory()];
	[panel setAllowsMultipleSelection:NO];
	[panel setCanChooseDirectories:NO];
	[panel setCanChooseFiles:YES];
	[panel setResolvesAliases:YES];
	
	[panel beginSheetModalForWindow:window completionHandler:^(NSInteger result) {
		if (result == NSFileHandlingPanelOKButton) {
			// We aren't allowing multiple selection, but NSOpenPanel still returns
			// an array with a single element.
			NSURL *imagePath = [[panel URLs] objectAtIndex:0];
			NSImage *image = [[NSImage alloc] initWithContentsOfURL:imagePath];
			NSLog(@"Image: %@", image);
			[image release];
		} else {
			[panel close];
		}

	}];
}

This will allow you to display an image picker sheet in Objective-C / Cocoa. Of note, this uses the new 10.6 beginSheetModalForWindow:completionHandler: method which takes a closure as its second argument. Much preferable in my opinion to passing @selectors around everywhere and having to keep track of what protocols your controllers should implement.

This example is for selecting an image, but you could repurpose this example for any kind of file.

[panel setAllowedFileTypes:[NSImage imageFileTypes]];