Entity Formatters

[bobbytables]

I'd like to get some input on formatters for entities, I have an idea.

module Entities
  class User < Grape::Entity
    formatter :timestamp

    expose :name
    expose :created_at, :formatter => :timestamp

    private

    def timestamp(date)
      date.strftime('%m/%d/%Y')
    end
  end
end

[mbleigh]

I like the idea, at least in theory. Implementation wise here would be my suggestion:

Rather than declaring formatter methods, let's just have a :format_with option that works like so:

1. If the option is set to a symbol, it does something like send(options[:format_with], value)
2. If the option is not a symbol, it does options[:format_with].call(value)

This way you can create custom formatters as lambdas, custom classes, or anything in between. You can also just use simple method-based ones like your example above.

REVERSER = lambda{|value| value.reverse}

module Entities
  class User < Grape::Entity
    expose :name
    expose :created_at, :format_with => :timestamp
    expose :backwards_name, :format_with => REVERSER

    private

    def timestamp(date)
      date.strftime('%m/%d/%Y')
    end
  end
end

[mbleigh]

I'm not 100% sold on :format_with, maybe :formatter was better.

[bobbytables]

Yeah I had the same thought on a lambda option as well. Although it would look odd if they supplied a block as well.

expose :created_at, :format_with => lambda {|d| d.strftime('%m/%d/%Y') } do |object,options|
end

I guess the options are:

• It raises saying you have to do one or the other
• The block is given the object after the formatter has had its way with it.