Question

So I had this bug where I had a method:

def returnArr
  [2,3,4]
end

And I did this:

returnArr = returnArr.first

returned an error stating that nilClass doesn’t have a method ‘first’

Moreover, after doing that line of code, and follow it up with this:

returnArr = returnArr().first

worked completely fine, and returnArr is now different from returnArr(). What is going on here?

Answer 1

When you have this line

 returnArr = returnArr.first

Ruby sees (and executes) this:

 returnArr = nil
 returnArr = returnArr.first

Before assigning value to a variable, this variable is initialized to nil. So, in this case, your local variable shadows your method. Without hints from your side, ruby can’t determine that actually you wanted to call the method. When you provide parentheses, ruby understands that local variable can’t have them and calls the method.

Don’t ever do this again. Especially in a real app.