Pourquoi apprendre DP ?

I think patterns as a whole can help people learn object-oriented thinking: how you can leverage polymorphism, design for composition, delegation, balance responsibilities, and provide pluggable behavior. Patterns go beyond applying objects to some graphical shape example, with a shape class hierarchy and some polymorphic draw method. You really learn about polymorphism when you’ve understood the patterns. So patterns are good for learning OO and design in general.