Ruby Datamapper .count always returns 0

问题

Whenever I try and count the returned records from datamapper it always returns as 0, whether there is a user or not.

User.count(:username=>params[:username])

class User
  include DataMapper::Resource

  property :id,  Serial
  property :username,  String, unique_index: true, required: true, length: 3..32
  property :password,  String, required: true, length: 5..64
  property :email,  String, unique_index: true, required: true, format: :email_address

end

回答1:

Can you try User.all(:username=>params[:username]) in console and then try

User.count(:username=>params[:username]) for that ENV

来源：https://stackoverflow.com/questions/12548032/ruby-datamapper-count-always-returns-0