简单如馅饼:

if !params[:one].nil? and !params[:two].nil?
  #do something...
elsif !params[:one].nil?
  #do something else...
elsif !params[:two].nil?
  #do something extraordinary...
end

如果你希望能够根据特定的缺失参数返回一个错误，而不必切换所有参数:

required_params = [:one, :two, :three]
required_params.each do |param|
  if params.has_key?(param)
    render json: { errors: "Missing parameter #{param.to_s}." }, :status => :bad_request 
    return
  end
end

params[:foo] ||= '默认值'

我刚在RubyInRails类上读到这个 http://api.rubyonrails.org/classes/Object.html#method-i-blank-3F

你可以用空白?方法，该方法等价于params[:one].nil?| | params[:]空虚吗?

(如)

if params[:one].blank? 
  # do something if not exist
else
  # do something if exist
end

你可以这样写得更简洁:

required = [:one, :two, :three]
if required.all? {|k| params.has_key? k}
  # here you know params has all the keys defined in required array
else
  ...
end

使用空白的?http://api.rubyonrails.org/classes/Object.html#method-i-blank-3F

unless params[:one].blank? && params[:two].blank?

将返回真，如果它为空或nil

也……这将不会工作，如果你是测试布尔值..自

>> false.blank?
=> true

那样的话你可以用

unless params[:one].to_s.blank? && params[:two].to_s.blank?