RUBY INHERITANCE MAINLY METHOD DISPATCH Created by Maciej Rząsa 

WHERE IS MY S U P E R ? 

CLASSES c l a s s A d e f f o o p r i n t " A " e n d e n d c l a s s B < A d e f f o o s u p e r p r i n t " B " e n d e n d p u t s B . n e w . f o o # > > " A B " 

MODULES m o d u l e I n c l u d e d e f f o o ; s u p e r ; p r i n t " I " ; e n d e n d m o d u l e P r e p e n d d e f f o o ; s u p e r ; p r i n t " P " ; e n d e n d c l a s s A d e f f o o ; p r i n t " A " ; e n d e n d c l a s s B < A i n c l u d e I n c l u d e p r e p e n d P r e p e n d d e f f o o ; s u p e r ; p r i n t " B " ; e n d e n d p u t s B . n e w . f o o # > > " A I B P " 

INCLUDE USAGE multiple inheritance (interface and implementation) use glue methods as interface (e.g. # e a c h for E n u m e r a b l e ) wrap inherited methods (aspect-oriented programming) 

WRAP INHERITED METHODS m o d u l e S a v e W r a p p e r d e f s a v e p u t s " s a v e c a l l i n g " s u p e r e n d e n d c l a s s A < A c t i v e R e c o r d : : B a s e i n c l u d e S a v e W r a p p e r e n d A . n e w . s a v e Strange? Rails is built this way ;-) 

PREPEND USAGE override methods not owned by the team (e.g. gems) alternative to reopening classes 

BONUS: DEFINING METHOD FOR ONE OBJECT m o d u l e I n c l u d e d e f f o o ; s u p e r ; p r i n t " I " ; e n d e n d m o d u l e P r e p e n d d e f f o o ; s u p e r ; p r i n t " P " ; e n d e n d c l a s s A d e f f o o ; s u p e r ; p r i n t " A " ; e n d e n d c l a s s B < A i n c l u d e I n c l u d e p r e p e n d P r e p e n d d e f f o o ; s u p e r ; p r i n t " B " ; e n d e n d b = B . n e w d e f b . f o o ; s u p e r ; p r i n t " N N N " e n d b . f o o # > > A I B P N N N 

DEFINING METHOD FOR ONE OBJECT: USAGE c l a s s A d e f s e l f . f o o p r i n t " A " e n d e n d 

PRIVATE VS PROTECTED 

PRIVATE c l a s s F o o p r i v a t e d e f b a r ; ' b a r ' e n d e n d c l a s s B a z < F o o d e f c h e c k _ b a r p u t s b a r p u t s s e l f . b a r r e s c u e p u t s ' s e l f p a r e n t N o M e t h o d E r r o r ' p u t s s e l f . q u x r e s c u e p u t s ' s e l f s e l f N o M e t h o d E r r o r ' p u t s P a r e n t . n e w . b a r r e s c u e p u t s ' n e w N o M e t h o d E r r o r ' p u t s P a r e n t . n e w . s e n d ( : b a r ) r e s c u e p u t s ' n e w N o M e t h o d E r r o r ' e n d p r i v a t e d e f q u x p u t s " q u x " e n d e n d B a z . n e w . c h e c k _ b a r # b a r # s e l f p a r e n t N o M e t h o d E r r o r # s e l f s e l f N o M e t h o d E r r o r # n e w N o M e t h o d E r r o r # b a r 

PROTECTED c l a s s F o o p r o t e c t e d d e f b a r ; ' b a r ' e n d e n d c l a s s B a z < F o o d e f c h e c k _ b a r p u t s b a r p u t s s e l f . b a r r e s c u e p u t s ' s e l f p a r e n t N o M e t h o d E r r o r ' p u t s s e l f . q u x r e s c u e p u t s ' s e l f s e l f N o M e t h o d E r r o r ' p u t s P a r e n t . n e w . b a r r e s c u e p u t s ' n e w N o M e t h o d E r r o r ' e n d p r o t e c t e d d e f q u x " q u x " e n d e n d B a z . n e w . c h e c k _ b a r # b a r # b a r # q u x # n e w N o M e t h o d E r r o r 

USAGE Protected comparison mutator methods for immutable objects internal API for an object (e.g. A c t i o n C o n t r o l l e r : : C a c h i n g ) Private Not tested methods Internals Other use # p u b l i c _ s e n d if in doubt ;-)