Use ActiveSupport Concern

[chulkilee]

It makes easy to use version class with different AR connection

[seanlinsley]

Can you give an example where you want to use this?

[chulkilee]

# with concerns - able to inherit custom Base class and share connections
module Foo
  class Base < ActiveRecord::Base
  end

  class Version < Base
    include PaperTrail::VersionConcern
  end

  class Document < Base
    has_paper_trail class_name: 'Foo::Version'
  end
end

module Bar
  class Base < ActiveRecord::Base
  end

  class Version < Base
    include PaperTrail::VersionConcern
  end

  class Document < Base
    has_paper_trail class_name: 'Bar::Version'
  end
end

Foo::Base.establish_connection({})
Bar::Base.establish_connection({})

Without concerns, version classes need to have it's own connection because PaperTrail::Version will use ActiveRecord::Base's connection. In addition it's difficult to add common behaviors or override ActiveRecord::Base method on Foo::Version using Foo::Base, because it inherits PaperTrail::Version (and ActiveRecord::Base), not Foo:Base.

# without concerns - need to inherit PaperTrail::Version
module Foo
  class Version < PaperTrail::Version
  end
end
module Bar
  class Version < PaperTrail::Version
  end
end

[Foo::Base, Foo::Version].each { |klass| klass.establish_connection({database: 'foo'}) }
[Bar::Base, Bar::Version].each { |klass| klass.establish_connection({database: 'bar'}) }

[batter]

So essentially this just makes it easy to use the gem with an application that makes multiple connections to databases. I think this makes sense then since it leaves the original functionality in tact but adds some flexibility. Any chance you could add a test or spec demonstrating the functionality if it's not too much trouble? If nothing else, it makes the use case easy to see for others going forward.

[jherdman]

FYI it's idiomatic usage of the AS::Concern module to define your class-level methods in a module called ClassMethods, and not in the included block. Example:

module VersionConcern
  included do
    # macros in here
  end

  module ClassMethods
    def some_class_level_method
    end
  end

  def some_instance_level_method
  end
end

[chulkilee]

PaperTrail::Version already uses the concern and all existing tests are passed - what kind of tests can we add? any suggestion?

@jherdman I'll make that change - thanks!

[batter]

@chulkilee - Probably just something similar to your example above, where a custom version class includes the PaperTrail::VersionConcern.

Also, it looks like the portion with the class methods needs to be modified a bit. The object_col_is_json? and object_changes_col_is_json? methods are now class methods. Does that fix all the failing tests?

[chulkilee]

@fullbridge-batkins fixed and added tests

[batter]

Yes I saw that, thank you, looks good. Was busy last week but going to merge this soon.

[batter]

Thanks a lot for this pull, very cool feature. I'm wondering if there is some way to document the usage of this on the README a bit better but perhaps the specs you provided make it obvious. By the way, I refactored the specs a little bit in 975e1bb so it is organized a bit better.

[chulkilee]

thanks!