grape的given

使用方式

given page: ->(v){v>1}, ref: ->(v){v=='history_price'} do
  # ....
end

将given条件保存到dependent_on

# grape-1.5.3/lib/grape/dsl/parameters.rb
def given(*attrs, &block)
  attrs.each do |attr|
    proxy_attr = first_hash_key_or_param(attr)
    raise Grape::Exceptions::UnknownParameter.new(proxy_attr) unless declared_param?(proxy_attr)
  end
  new_lateral_scope(dependent_on: attrs, &block)
end

检查dependent_on

# grape-1.5.3/lib/grape/validations/params_scope.rb
def meets_dependency?(params, request_params)
  return true unless @dependent_on

  if @parent.present? && !@parent.meets_dependency?(@parent.params(request_params), request_params)
    return false
  end

  return params.any? { |param| meets_dependency?(param, request_params) } if params.is_a?(Array)

  # params might be anything what looks like a hash, so it must implement a `key?` method
  return false unless params.respond_to?(:key?)

  @dependent_on.each do |dependency|
    if dependency.is_a?(Hash)
      dependency_key = dependency.keys[0]
      proc = dependency.values[0]
      return false unless proc.call(params.try(:[], dependency_key))
    elsif params.respond_to?(:key?) && params.try(:[], dependency).blank?
      return false
    end
  end

  true
end