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How to create own utility methods for your Rails application

igorkasyanchuk profile image Igor Kasyanchuk ・2 min read

Hello,

As a developer, I need from time to time to quickly execute SQL, or check something in DB, truncate a table, etc when I'm in the rails console.

You may already know about using ActiveRecord::Base.connection.execute("SQL query") solution, but I must admit I'm a lazy developer when it comes to doing routine tasks or things where I need to type long pieces of code. And actually a snippet of code above is not everything that you need to type, you may also need to add .to_a to see the result of the query.

I know the following rule:

laziness is the engine of progress!

So, I tried to solve my issue as a developer and create an open-source solution to use it from project to project: https://github.com/igorkasyanchuk/execute_sql

This is a demo of how it works:
Demo

I'll explain how it works.

Step of creation gem I'll skip, but basically you need to create a new gem (rails plugin new <name>).

Now we need to understand how to add our own method just in the rails console.

module ExecuteSql
  class Railtie < ::Rails::Railtie

    console do
      TOPLEVEL_BINDING.eval('self').extend ExecuteSql::ConsoleMethods
    end

  end
end

This is a piece of code from my gem. You can see that Rails provides a helper method console where you can pass the code which will be executed when you starting rails c.
In our case this is TOPLEVEL_BINDING.eval('self').extend ExecuteSql::ConsoleMethods.

In case you have wondered, what this top-level constant TOPLEVEL_BINDING is all about better to check sample of usage below:

a = 42
p binding.local_variable_defined?(:a) # => true
p TOPLEVEL_BINDING.local_variable_defined?(:a) # => true

def example_method
  p binding.local_variable_defined?(:a) # => false
  p TOPLEVEL_BINDING.local_variable_defined?(:a) # => true
end

example_method

More details about TOPLEVEL_BINDING you can find here.

[11] pry(main)> TOPLEVEL_BINDING.eval('self')
=> main
[12] pry(main)> TOPLEVEL_BINDING
=> #<Binding:0x0000000001350b00>

As you can see TOPLEVEL_BINDING.eval('self') is basically the context of our console app.

So the last thing for us to do is to extend the main app with our class methods from ExecuteSql::ConsoleMethods module, source code is here.

This module inside is responsible for queries DB, and basically I took most of the code from my other gem rails_db and printing results using terminal-table gem.

Now my life is easier :)

And I hope you can implement your own utility methods.

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