The quick way to do it besides going to the file you want to check, use
 pry(main)> User.methods(false).count => 100
User model responds to 100 methods.
 pry(main)> User.instance_methods(false).count => 0
Let's remember Sandi Metz rules:
Prefer small methods. Between one and five lines is best.
Prefer small classes with a single, well-defined responsibility. When a class exceeds 100 lines, it may be doing too many things.
That's all folks!, thank you very much for reading, follow me on twitter @zazvick