Set of enum

[sled]

A flood of questions:

• How can we realise something like a set of a specific type, i.e
  attribute :selected_months, :set, class_name: Porro::Types::Enum.new(1..12)
• How to set a default value for an attribute, e.g
  attribute :something, :string, default: 'a meaningful default'
• Shouldn't we initialize an empty collection by default, e.g
  attribute :friends, :set, class_name: :string causes an_instance.friends to return nil wouldn't it make more sense to have something like an_instance.friends << "barry the dog"

[lwe]

@sled using the alternative DSL a lot of these are already possible, will give more input tomorrow.

[sled]

thanks! the first one I already figured out how to do:

attribute :peak_months, Porro.set(Porro::Types::Enum.new(1..12))

2.3.0 :111 > a.peak_months = Set.new([55,1,66,12])
 => #<Set: {55, 1, 66, 12}>
2.3.0 :112 > a.peak_months
 => #<Set: {1, 12}>

However it still allows adding invalid values afterwards (due to the naked Set returned):

2.3.0 :113 > a.peak_months << 55
 => #<Set: {1, 12, 55}>
2.3.0 :114 > a.peak_months
 => #<Set: {1, 12, 55}>

Would be cool if we could find an easy way around this (immutable? cloning? overloading?), otherwise we could rely on validations.

[lwe]

Jup, was thinking about using a proxy or something, but as there is an unlimited number of methods which modify a Set/Array/Enumerable I decided if's not worth the trouble. Yes, we should handle this using validations, makes more sense.

Isn't there a Default.new wrapper class already?

[lwe]

and yes I agree we should probably provide an empty list by default, care to take a PR?