Ruby on Rails: Execute Logic Based on Selected Menu

Question

I have a class that I use to contain select menu options for property types. It works fine. However, I need to be able to verify the selection and perform specific logic based on the selected option. This needs to happen in my Ruby code and in JavaScript.

Here is the class in question:

class PropertyTypes

    def self.[](id)
        @@types[id]
    end

    def self.options_for_select
     @@for_select
    end

    private
    @@types = {
            1 => "Residential",
            2 => "Commercial",
            3 => "Land",
            4 => "Multi-Family",
            5 => "Retail",
            6 => "Shopping Center",
            7 => "Industrial",
            8 => "Self Storage",
            9 => "Office",
            10 => "Hospitality"
    }

    @@for_select = @@types.each_pair.map{|id, display_name| [display_name, id]}
end

What is the best way to verify the selection? I need to perform specific logic and display user interface elements based on each type of property type.

Since I am storing the id, I would be verifying that the id is a particular property type. Something like:

PropertyTypes.isResidential?(id)

Then this method would look like this:

def self.isResidential?(id)
    @@types[id] == "Residential"
end

But now I am duplicating the string "Residential".

For JavaScript, I assume I would make an ajax call back to the model to keep the verification code DRY, but this seems like over kill.

Do I need to manually create a verification method for each property type or can I use define_method?

This seems so basic yet I am confused and burned out on this problem.

Thanks

=== Here's my solution:

class << self
@@types.values.each do |v|
  # need to remove any spaces or hashes from the found property type
   v = v.downcase().gsub(/\W+/, '')

   define_method "is_#{v}?", do |i|
     type_name = @@types[i]
     return false if type_name == nil #in case a bogus index is passed in
     type_name = type_name.downcase().gsub(/\W+/, '')
     type_name == v
   end
 end
end

score 1 · Answer 1 · answered Sep 10 '11 at 16:08

It sounds like you can benefit from some Ruby meta-programming. Try googling "ruby method_missing". You can probably do something quick & dirty along the lines of:

class PropertyTypes
 def method_missing(meth, *args, &block)
    if meth.to_s =~ /^is_(.+)\?$/
      @@types[args.first] == $1
    else
      super
    end
  end
end

score 0 · Accepted Answer · answered Sep 10 '11 at 16:26

0

On the ruby side you could also use something like this to define dynamically these methods:

class << self
  @@types.values.each do |v|
    define_method "is_#{v}?", do |i|
      @@types[i] == v
    end
  end
end

answered Sep 10 '11 at 16:26

paozac

223
2
7

Awesome! I tried both techniques mentioned (define_missing and define_method) and went with define_method as there is no need to deal with the respond_to? method. – tollbooth Sep 10 '11 at 18:05
This is a good article on working with [method_missing](http://stackoverflow.com/questions/291132/method-missing-gotchas-in-ruby) – tollbooth Sep 10 '11 at 18:12

Ruby on Rails: Execute Logic Based on Selected Menu

2 Answers2