I heard a lot about Duck Types in Rails but I have never saw how can I used in a real-time application. Today I will show you how to use duck types in examples.
Duck Typing is a style of dynamic typing in which an object’s methods and properties determine the valid semantics, rather than its inheritance from a particular class or implementation of a specific interface.
This sounds a bit weird for me, lets make an example. For instance you have a class that responsible for generating some View-presenter data according to objects that you pass
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
In some day you could came up to such solution. And on what you should take a look This violates SOLID principles.
- Why presenter class should know about view representation about each class?
- We did not make any modifications with data that came up from class, than why we cannot move this method to class itself?
Let’s refactoring this:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
If subject will not implement description than rails will raise an exception. Next iteration of refactoring
1 2 3 4 5
Congratulation you successfully implement Duck type :) But now our presenter looks like lazy class. So this class could be totally removed.
If something looks like a duck and quack like a duck than it is a duck. Also it will be good to test such Ducks using rspec shared_examples