Learn Ruby on Rails
If you take the time to fully understand Ruby before you learn Rails; then learning Rails will become a piece of cake.
Whether you build controller, action or else, it will all come down to Ruby.
There is list of online resources you can use.
1. Learn to program
http://zetcode.com/lang/rubytutorial/
2. Object-oriented programming in Ruby
http://zetcode.com/lang/rubytutorial/oop/
http://zetcode.com/lang/rubytutorial/oop2/
3. Learning Ruby the Hard Way
https://learnrubythehardway.org/book/
4. Try Ruby
https://try.ruby-lang.org/
5. Ruby Programming
Learn Rails
1. The Ruby on Rails Guide
http://guides.rubyonrails.org/
2. Ruby on Rails Tutorial
https://www.railstutorial.org/book
4. Ruby on Rails Tutorial Part 1
5. Ruby on Rails Tutorial Part 2
6. Ruby on Rails Tutorial Part 3
