ContentfulModel::Base doesn't provide a #hash method

[georgebrock]

ContentfulModel::Base doesn't provide a #hash method, so model instances cannot be effectively used as keys in Hashes, or easily filtered for duplicates.

For example, I have a Requirement model which has_one Category. After loading my requirements, I group them by category:

requirements.group_by(&:category)
  # => {<Category> => [<Requirement>, <Requirement>, …], …}

For the results of a single query, this works fine. However, sometimes I want to combine the results of two queries, to simulate a logical OR:

(some_requirements + other_requirements).uniq.group_by(&:category)

This throws up two problems, both arising from the lack of #hash:

1. Duplicate requirements from the two queries are different objects, and since they inherit the default implementation of #hash, they're not filtered out by #uniq.
2. Any category that was present in both sets of results ends up as two different keys in the resulting Hash, again because they are different objects.

Possible solutions

In my app, I added #hash and #eql? methods based closely on ActiveRecord's implementation:

  def eql?(other)
    super || other.instance_of?(self.class) && id.present? && other.id == id
  end

  def hash
    if id.present?
      self.class.hash ^ id.hash
    else
      super
    end
  end

[dlitvakb]

Hey @georgebrock,

Thanks for the suggestion, I'm currently implementing the upgrade to the 2.0 CDA SDK and implemented a similar solution to this.

The release will be coming up in the next few weeks, with the initial PR coming out tomorrow.

Cheers