Newbie syntax questions

Ruby
1

Hi

In the ‘test/unit’ library the file unit.rb contains the following code.

module Test
module Unit
def self.run=(flag)
@run = flag
end

def self.run?
  @run ||= false
end

end
end

at_exit do
unless $! || Test::Unit.run?
exit Test::Unit::AutoRunner.run($0 != “-e” && $0)
end
end

Could someone please explain the following:

  1. Why is there an equals sign in the code “def self.run=(flag)” and
    what
    does it do?

  2. Why is there an equals sign in the code “@run ||= false” and what
    does
    it do?

  3. Why is the ‘run’ member of the ‘Unit’ module accessible on the line "
    unless $! || Test::Unit.run?"? Doesn’t this require the attr_reader
    syntax
    in the module?

  4. What does “$0 != “-e” && $0” mean and do?

Thanks