Ruby on Rails: How to check if the Model Exists

Question

I want to know how to check if the model already exists in the project or not?

When user tries to create a model programatically using the same model name, need to check if it already exists or not?

Plated

Answer 1

defined? ModelName will return "constant" if model defined.

Doughboy

defined? doesn't seem to return consistent results. Please check the code below: ` $ rails c Loading development environment (Rails 4.2.0) 2.2.1 :001 > defined?(User) => "constant" 2.2.1 :002 > defined?(AuthenticationToken) => nil 2.2.1 :003 > AuthenticationToken => AuthenticationToken (call 'AuthenticationToken.connection' to establish a connection) 2.2.1 :004 > defined?(AuthenticationToken) => "constant" 2.2.1 :005 > ` – Annul

Agree^ it seems that some constants are only loaded after referenced? – Spieler

Here's a link to more info on the defined? operator: ruby-doc.com/docs/ProgrammingRuby/html/tut_expressions.html#UG – Girandole

Answer 2

Since defined? is problematic (see @Jiggneshh Gohel's comment), perhaps you can check the filenames in the models dir.

files = Dir[Rails.root + 'app/models/*.rb']
models = files.map{ |m| File.basename(m, '.rb').camelize }

models.include? "User" => true

Induct

Answer 3

Another option is use exists

Return false if there is no column in the model.

Nakisha