Which is correct REPL or command-line?

Question

when i write method missing in Object class i'm getting the output different in each interface.

the code is

class Object
  def method_missing(hgh)
    puts self
  end
end

when i use REPL like irb, i get

when i use the command line, i get no error, any reasons would be helpful, thanks in advance

Answer 1

The tl;dr answer is that both are correct. Just more stuff happen in the REPL.

---

When you run the code from the command line like:

ruby script.rb

All that happens is that it's evaluated.

Whereas REPLs like IRB read your input, evaluate it and print it in a loop.

In this case evaluating your code literally broke the REPL and resulted in the subsequent print failing.

---

Now you may be a bit confused by this. "There is a print in both cases, I use puts!". The print I'm referring to here is the result that gets visualised after each evaluation. In this case the method definition result (=> :method_missing).

---

It might not only be the printing itself. It can be the ton of other under the hood code that the REPL has to execute to keep state like "what code was defined on which line" and so on.

Think of what you just did - you made it so that every object has every method possible to return nil. That is not just for the code you write in the REPL. It's for the code of the REPL itself as well.