How can I create an object using the content inside a variable in Ruby?

Question

Consider I have a variable class_name. class_name can hold string values like blog, comment etc. based on the value inside class_name I need to create respective object.

If class_name is blog, I need to create a blog object. How can I achieve this without using a switch?

Answer 1

You'd use the camelize and constantize methods thusly:

klass = class_name.camelize.constantize
thing = klass.new

If you started with 'blog' in class_name, your klass would end up as Blog. If your string is actually 'Blog', then:

klass = class_name.constantize
thing = klass.new

Both camelize and constantize are Rails-specific but I see the "ruby-on-rails" tag so we're in Rails-land.

Answer 2

You can use Kernel.const_get but case is important.

a = 'Blog'
b = Kernel.const_get(a).new