Renamed `- (void)_show` method to `- (void)showInternal`. Apple's "Coding Guidelines for Cocoa" clearly state to "[…] avoid the use of the underscore character as a prefix meaning private in method names.", even more so: "Apple reserves the use of this convention."
Moved UI element initialization into their own (and thus overridable) class methods.
Blocks must be copied, not retained. Fixed.