By Joe Ferris, Harlow Ward
You construct internet functions, and also you love Ruby on Rails since it provides
a framework for constructing purposes which are are quick, enjoyable, and simple to change.
Over time those purposes can turn into bloated, improvement slows down,
and adjustments to the codebase turn into painful.
This publication was once written that can assist you discover ways to realize rising difficulties in your
codebase we’ll bring the strategies for solving them, and holding an
application that may be enjoyable to paintings on for years yet to come.
Read or Download Ruby Science PDF
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Extra info for Ruby Science
Sample text
Text_field :text %> <% end -%> In the previous example, we moved type-specific code into Question subclasses. However, moving view code would violate MVC (introducing Divergent Change into the subclasses), and more importantly, it would be ugly and hard to understand. Rails has the ability to render views polymorphically. A line like this: <%= render @question %> Will ask @question which view should be rendered by calling to_partial_path. As subclasses of ActiveRecord::Base, our Question subclasses will return a path CHAPTER 14.
REPLACE CONDITIONAL WITH POLYMORPHISM 39 Replace Type Code With Subclasses Let’s replace this case statement with polymorphism by introducing a subclass for each type of question. Our Question class is a subclass of ActiveRecord::Base. If we want to create subclasses of Question, we have to tell ActiveRecord which subclass to instantiate when it fetches records from the questions table. The mechanism Rails uses for storing instances of different classes in the same table is called Single Table Inheritance.
Rails will take care of most of the details, but there are a few extra steps we need to take when refactoring to Single Table Inheritance. Single Table Inheritance (STI) The first step to convert to STI is generally to create a new subclass for each type. rb def summary case question_type when 'MultipleChoiceQuestion' summarize_multiple_choice_answers when 'OpenQuestion' summarize_open_answers when 'ScaleQuestion' summarize_scale_answers end end CHAPTER 14. update(<<-SQL) UPDATE questions SET question_type = REPLACE(question_type, 'Question', '') SQL end end See commit b535171 for the full change.
Ruby Science by Joe Ferris, Harlow Ward
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