Ruby on rails 铁轨：；NoMethodError：未定义的方法`ConstructionKDTree'；对于#<；类别：0x0000104B1F760>&引用；

您好，我在rails中有3个文件，如下所示： 1） 位于“app/controller/listings\u controller.rb”

现在我正在尝试测试

constructKDTree

的方法实现，因此我转到rails控制台并尝试了以下命令：

1.9.2-p290 :001 > @lc = ListingsController.new
 => #<ListingsController:0x00000104f3e288 @_routes=nil, @_action_has_layout=true, @_headers={"Content-Type"=>"text/html"}, @_status=200, @_request=nil, @_response=nil> 

1.9.2-p290 :002 > @lc.index

1.9.2-p290:001>@lc=ListingsController.new
=>#“text/html”}、@_status=200、@_request=nil、@#u response=nil>
1.9.2-p290:002>@lc.index

但我得到了这个错误：

NoMethodError: undefined method `constructKDTree' for #<Class:0x00000104b1f760>
from /Users/AM/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.2.1/lib/active_record/dynamic_matchers.rb:50:in `method_missing'
from /Users/AM/Documents/RailsWS/cmdLineWS/Businesses/app/controllers/listings_controller.rb:20:in `index'
from (irb):2
from /Users/AM/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.2.1/lib/rails/commands/console.rb:47:in `start'
from /Users/AM/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.2.1/lib/rails/commands/console.rb:8:in `start'
from /Users/AM/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.2.1/lib/rails/commands.rb:41:in `<top (required)>'
from script/rails:6:in `require'
from script/rails:6:in `<main>'

NoMethodError:#
from/Users/AM/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.2.1/lib/active\u record/dynamic\u matchers.rb:50:in'method\u missing'
from/Users/AM/Documents/RailsWS/cmdLineWS/business/app/controllers/listings_controller.rb:20:in'index'
来自（irb）：2
from/Users/AM/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.2.1/lib/rails/commands/console.rb:47:in'start'
from/Users/AM/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.2.1/lib/rails/commands/console.rb:8:in'start'
from/Users/AM/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.2.1/lib/rails/commands.rb:41:in`'
来自脚本/rails:6:in'require'
来自脚本/rails:6:in`'

我做错了什么？

这是对类方法的调用：

这是实例方法的定义：

您希望

constructKDTree

成为类方法，因此需要这样说：

def self.constructKDTree
  #...

---

您在清单中将

constructKDTree

定义为一个实例方法。因此，该方法仅适用于类的实例，而不适用于类本身

根据您实际想要实现的内容，您可以像在下面的代码中那样将该方法设置为类方法，或者您可以创建

列表

类的新实例，并在该实例上调用该方法

class Listing < ActiveRecord::Base
  def self.constructKDTree
    @contents = self.all
    @kdTree = KDTree.new(@contents) 
  end
end

---

嗨，谢谢。我来自Java背景，学习Ruby。那么类级方法和Java中的静态方法一样吗？@banditKing:是的，这是最接近的了。

NoMethodError: undefined method `constructKDTree' for #<Class:0x00000104b1f760>
from /Users/AM/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.2.1/lib/active_record/dynamic_matchers.rb:50:in `method_missing'
from /Users/AM/Documents/RailsWS/cmdLineWS/Businesses/app/controllers/listings_controller.rb:20:in `index'
from (irb):2
from /Users/AM/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.2.1/lib/rails/commands/console.rb:47:in `start'
from /Users/AM/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.2.1/lib/rails/commands/console.rb:8:in `start'
from /Users/AM/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.2.1/lib/rails/commands.rb:41:in `<top (required)>'
from script/rails:6:in `require'
from script/rails:6:in `<main>'

@tree = Listing.constructKDTree

def constructKDTree
  @contents = self.all
  @kdTree = KDTree.new(@contents) 
end

def self.constructKDTree
  #...

class Listing < ActiveRecord::Base
  def self.constructKDTree
    @contents = self.all
    @kdTree = KDTree.new(@contents) 
  end
end

listing = Listing.new
@tree = listing.constructKDTree