How to write same requirements for multiple routes e.g. POST, PUT? (Ruby Grape)

Question

How can I avoid duplicate code?

resource 'api/publication/:publicationName' do

  params do
    requires :type, type: String, regexp: /^(static|dynamic)$/i
    requires :name, type: String, regexp: /^[a-z0-9_\s]+$/i
    requires :liveStartDate, type: String, regexp: dateRegexp
    optional :liveEndDate, type: String, regexp: dateRegexp
    requires :query, type: String
  end
  post '/dynamic' do
    authenticate!
    save_or_update(params)
  end

  params do
    requires :type, type: String, regexp: /^(static|dynamic)$/i
    requires :name, type: String, regexp: /^[a-z0-9_\s]+$/i
    requires :liveStartDate, type: String, regexp: dateRegexp
    optional :liveEndDate, type: String, regexp: dateRegexp
    requires :query, type: String
  end
  put '/dynamic/:id' do
    authenticate!
    save_or_update(params)
  end

end

Answer 1

In more recent versions of Grape, you can create reusable named groups of parameters. For example:

resource 'api/publication/:publicationName' do
  helpers do
    params :common do
      requires :type,          type: String, regexp: /^(static|dynamic)$/i
      requires :name,          type: String, regexp: /^[a-z0-9_\s]+$/i
      requires :liveStartDate, type: String, regexp: dateRegexp
      optional :liveEndDate,   type: String, regexp: dateRegexp
      requires :query,         type: String
    end
  end

  params do
    use :common
  end
  post '/dynamic' do
    authenticate!
    save_or_update(params)
  end

  params do
    use :common
  end
  put '/dynamic/:id' do
    authenticate!
    save_or_update(params)
  end
end

One advantage of doing things this way is that you can mix different groups of parameters by including multiple use statements for different named params.

Answer 2

Try this:

resource 'api/publication/:publicationName' do
  common_params = Proc.new do
    requires :type,          type: String, regexp: /^(static|dynamic)$/i
    requires :name,          type: String, regexp: /^[a-z0-9_\s]+$/i
    requires :liveStartDate, type: String, regexp: dateRegexp
    optional :liveEndDate,   type: String, regexp: dateRegexp
    requires :query,         type: String
  end

  params(&common_params)
  post '/dynamic' do
    authenticate!
    save_or_update(params)
  end

  params(&common_params)
  put '/dynamic/:id' do
    authenticate!
    save_or_update(params)
  end
end