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Instantiate a Class from a String in Rails

Rails classes need to be called dynamically sometimes. Learn how to do it using the constantize inflector.

Sometimes you want your class names to be dynamic. Rails has a nice constantize inflector that makes this easy.

In the simplest of examples, let's just say you have a "post" string and you want to load the Post class from it. Something like the following should work great.

str = "post"
new_class_instance = str.constantize.new

We can get a little wild. Let's say you have a multi-word string and want to constantize and then instantiate it.

str = "posts controller"
new_class_instance = str.titleize.gsub(/\ /, '').constantize.new

Essentially, this just shows you want a properly-cased string (the string equivalent of the class name) before you call constantize.

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