Ruby命令行解析

Question

class Test

    options = Trollop::options do
        opt :mode, "Select script mode", :default => 0
        opt :net, "Internal IP range", :type => :string
    end

@options = options

    def test
        pp @options
    end
end

Why does @options return nil when I call test() ?

I've also tried setting @options to instance when Trollop is first called. I need to be able to pass the options hash returned from Trollop into different methods in the class.

Answer 1

If you really want to use a class instance variable for option storage then this would work:

class Test
   @options = Trollop::options ...

   class << self
     attr_accessor :options
   end

   def test
     pp Test.options
     # or self.class.options
   end
 end

 # And this will work too..
 pp Test.options

Otherwise you might want to use a class variable @@options or constant, like the other ones pointed out, instead.

Answer 2

What you have here is a scoping issue. @options in class context is an instance variable of the class. In test , you access the instance variable @options in the current instance. Try constants, aka OPTIONS , which have lexical scoping. Maybe someone else knows of a cleaner solution to this.

Answer 3

As Tass points out, changing @options to OPTIONS is one way.

You could also use @@options; it's a class variable in either context.

Answer 4

You're adding a class instance variable, but when you reference it in the method, you're referencing what looks like an instance variable.

First, you might want to instead use a class variable rather than a class instance variable. There's some information on the distinction here .

class Test

    @@options = Trollop::options do
        opt :mode, "Select script mode", :default => 0
        opt :net, "Internal IP range", :type => :string
    end


    def test
        pp @@options
    end
end

Test.test

The other option is to instantiate your class variable when initializing the test object, as below:

class Test

    def initialize
        @options = Trollop::options do
            opt :mode, "Select script mode", :default => 0
            opt :net, "Internal IP range", :type => :string
        end
    end


    def test
        pp @options
    end
end

t = Test.new
t.test