What is the difference between these two ruby functions?

Question

Function GetTitle when called from ruby shell throws an error "uninitialized constant GetTitle"

While full_title is working fine.

What is the problem with the GetTitle?

def GetTitle(pageTitle = '')
  baseTitle = "Base Title"
  if pageTitle.empty?
    baseTitle
  else
    pageTitle + " | " + baseTitle
  end
end

def full_title(page_title = '')
  base_title = "Ruby on Rails Tutorial Sample App"
  if page_title.empty?
    base_title
  else
    page_title + " | " + base_title
  end
end

Answer 1

In Ruby, as per convention, constants begin with an uppercase letter. So when you call GetTitle its being treated as a constant and you get appropriate error (since there is no such constant). However if you call it with a parameter, it will work. This is because of the presence of parameter Ruby is interpreting it as a method. Here:

GetTitle
# NameError: uninitialized constant GetTitle
GetTitle('abc')
#=> "abc | Base Title"

You can make Ruby believe its a method by using empty parenthesis too:

GetTitle()
#=> "Base Title"

This answer explains it beautifully.