Question

I am trying to write a script in Ruby which interactively generate some input data for a program. The idea is use QtRuby when it exists, otherwise console is used. What I tried is to

begin
  require "Qt4"
rescue LoadError => load_err
  puts "Qt not found, using console"
end

class ConsoleDefine
  # console code
end

class QtDefine < Qt::Widget
  # GUI code
end

but the interpreter refused my code when Qt4 does not exist. is there a way to deal it similar to C++, like:

#ifdef QT4
class qt4gui 
{
    // some code
};
#else
class qt4gui
{
    // dummy
};
#endif // Qt4

Answer 1

Use require to your advantage:

begin
  require "Qt4"
  require "my_lib/qt4"
rescue LoadError => load_err
  puts "Qt not found, using console"
  require "my_lib/console"
end

Create the two files:

# my_lib/console.rb
class ConsoleDefine
  # console code
end

# my_lib/qt4.rb
class QtDefine < Qt::Widget
  # GUI code
end