Will_paginate和DataMapper只能在irb中工作

Question

我试图让will_paginate和Sinatra一起工作，并且我对will_paginate和DataMapper有一个问题。所以我有一个代码：

require 'data_mapper' 
require 'will_paginate' 
require 'will_paginate/data_mapper' 
class User 
    include DataMapper::Resource 

    property :id, Serial # primary serial key 
    property :username, String, length: 5..15, unique: true 
    property :fullname, String, length: 5..25 
    property :email, String, required: true, unique: true, format: :email_address 
    property :hashed_password, String 
    property :created_at, Time, required: true 
    property :auth_token, String 
    property :locale, String 

    has n, :items 
end 

class Item 
    include DataMapper::Resource 
    property :id, Serial 
    property :question, String, required: true 
    property :answer, String, required: true 
    property :ef, Float 
    property :interval, Float 
    property :created_at, Time 
    property :updated_at, Time 
    property :reviev_at, Time 

    belongs_to :user 
end 

DataMapper::setup(:default, "sqlite3://#{File.expand_path(File.dirname(__FILE__))}/database2.db") 
DataMapper.finalize 
DataMapper.auto_upgrade! 

u = User.first 
p = u.items.paginate(page: 1) 
puts p.total_entries 

并运行它会导致一个问题：

/home/changs/src/PwS/vendor/bundle/ruby/1.9.1/gems/dm-core-1.1.0/lib/dm-core/query.rb:942:in `assert_valid_order': +options[:order]+ should not be empty if +options[:fields] contains a non-operator (ArgumentError) 
    from /home/changs/src/PwS/vendor/bundle/ruby/1.9.1/gems/dm-core-1.1.0/lib/dm-core/query.rb:773:in `block in assert_valid_options' 
    from /home/changs/src/PwS/vendor/bundle/ruby/1.9.1/gems/dm-core-1.1.0/lib/dm-core/query.rb:766:in `each' 
    from /home/changs/src/PwS/vendor/bundle/ruby/1.9.1/gems/dm-core-1.1.0/lib/dm-core/query.rb:766:in `assert_valid_options' 
    from /home/changs/src/PwS/vendor/bundle/ruby/1.9.1/gems/dm-core-1.1.0/lib/dm-core/query.rb:363:in `update' 
    from /home/changs/src/PwS/vendor/bundle/ruby/1.9.1/gems/dm-core-1.1.0/lib/dm-core/query.rb:386:in `merge' 
    from /home/changs/src/PwS/vendor/bundle/ruby/1.9.1/gems/will_paginate-3.0.2/lib/will_paginate/data_mapper.rb:54:in `total_entries' 
    from test.rb:39:in `<main>' 

但如果我注释掉最后三行它工作在IRB休耕：

ruby-1.9.2-p290 :001 > require './test' # file with deleted last 3 lines 
=> true 
ruby-1.9.2-p290 :002 > u = User.first 
=> #<User @id=1 @username="Testt" @fullname="tetestse" @email="test@wp.pl" @hashed_password=nil @created_at=2011-11-14 00:00:00 +0100 @auth_token=nil @locale=nil> 
ruby-1.9.2-p290 :003 > p = u.items.paginate(page: 1) 
=> [#<Item @id=1 @question="A" @answer="B" @ef=nil @interval=nil @created_at=2011-11-14 00:00:00 +0100 @updated_at=2011-11-14 00:00:00 +0100 @reviev_at=nil @user_id=1>, #<Item @id=2 @question="C" @answer="D" @ef=nil @interval=nil @created_at=2011-11-14 00:00:00 +0100 @updated_at=2011-11-14 00:00:00 +0100 @reviev_at=nil @user_id=1>] 
ruby-1.9.2-p290 :004 > puts p.total_entries 
2 
=> nil 

Answer 1

这发生的原因是从脚本调用p.total_entries时未加载p。在irb打印后，设置p后的值会导致它被加载。您可以致电total_entries，这样才解决它通过重装：

u = User.first 
p = u.items.paginate(page: 1) 
p.reload 
puts p.total_entries 

对我来说，这似乎是应该报告在will_paginate的错误。