Create a radio button matrix in Cocoa

I want to create a matrix 开发者_如何学JAVAof 3 radio buttons in my OS X app. Does anyone know how to do this programatically?

NSButtonCell *prototype = [[NSButtonCell alloc] init];
[prototype setTitle:@"Watermelons"];
[prototype setButtonType:NSRadioButton];
NSRect matrixRect = NSMakeRect(20.0, 20.0, 125.0, 125.0);
NSMatrix *myMatrix = [[NSMatrix alloc] initWithFrame:matrixRect
                                                mode:NSRadioModeMatrix
                                           prototype:(NSCell *)prototype
                                        numberOfRows:3
                                     numberOfColumns:1];
[[[typeField window] contentView] addSubview:myMatrix];
NSArray *cellArray = [myMatrix cells];
[[cellArray objectAtIndex:0] setTitle:@"Apples"];
[[cellArray objectAtIndex:1] setTitle:@"Oranges"];
[[cellArray objectAtIndex:2] setTitle:@"Pears"];
[prototype release];
[myMatrix release];

code snippet from Using Radio Buttons in Apple's docs.

Note the usage of prototype NSButtonCell - that way we can tell NSMatrix that buttons of NSRadioButton type should be used (which cannot be done using just cell's class it seems)