控制器中的助手 - Rails 3

发布于 2024-12-27 18:11:51 字数 571 浏览 2 评论 0原文

我从 Rails 2.x 迁移到 3.x。现在当调用控制器方法时抛出

nil:NilClass 的未定义方法“my_helper_method”

MyController.rb

class MyController < ApplicationController
    def foo
      @template.my_helper_method
    end
end

MyControllerHelper.rb

class MyControllerHelper
    def my_helper_method
      puts "Hello"
    end
end

ApplicationController

class ApplicationController < ActionController::Base
   helper :all
end

如何让它工作？

原文

I migrated from rails 2.x to 3.x. Now when calling a controller method throws

undefined method `my_helper_method' for nil:NilClass

MyController.rb

class MyController < ApplicationController
    def foo
      @template.my_helper_method
    end
end

MyControllerHelper.rb

class MyControllerHelper
    def my_helper_method
      puts "Hello"
    end
end

ApplicationController

class ApplicationController < ActionController::Base
   helper :all
end

How to get this working?

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放赐 2025-01-03 18:11:51

这实际上在另一篇SO帖子中得到了回答：Rails 3：@template变量内部控制器为零

本质上，您可以将@template替换为view_context

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诺曦 2025-01-03 18:11:51

@template 是一个对象，在您的情况下是nil。如果此对象中没有方法 (my_helper_method)，则无法调用它（尤其是当它为 nil 时）。

在帮助器中定义的方法像常规方法一样被调用。但不是在控制器中，它们是在视图中调用的。您的 helper :all 只是使所有助手都可用于视图。

因此，在您看来： my_helper_method :arg1, :arg2

如果您的对象需要一个方法 (@template)，则需要为您的对象提供此方法。

示例：

class Template < ActiveRecord::Base

  def my_helper_method
    # do something on a template instance
  end

end


class MyController < ApplicationController
  def foo
    @template = Template.first
    @template.my_helper_method # which actually isn't a helper
  end
end

助手的作用：

module MyHelper
  def helper_method_for_template(what)
  end
end

# in your view
helper_method_for_template(@template)

混合助手（将视图助手与视图和模型混合时，请注意代码中是否会出现混乱）

class Template < ActiveRecord::Base
  include MyHelper

  # Now, there is @template.helper_method_for_template(what) in here. 
  # This can get messy when you are making your helpers available to your
  # views AND use them here. So why not just write the code in here where it belongs
  # and leave helpers to the views? 
end

@template is an object, in your case nil. If this object doesn't has the method (my_helper_method) in it, you cannot call it (especially not if it is nil).

Methods defined in helpers are called like regular methods. But not in controllers, they are called in views. Your helper :all just makes all helpers available to the views.

So, in your view: my_helper_method :arg1, :arg2

IF you need a method for your object (@template), you need to give your object this method.

Example:

class Template < ActiveRecord::Base

  def my_helper_method
    # do something on a template instance
  end

end


class MyController < ApplicationController
  def foo
    @template = Template.first
    @template.my_helper_method # which actually isn't a helper
  end
end

What helpers do:

module MyHelper
  def helper_method_for_template(what)
  end
end

# in your view
helper_method_for_template(@template)

Mixing in a helper (be aware of having a mess in your code when mixing view helpers with views and models)

class Template < ActiveRecord::Base
  include MyHelper

  # Now, there is @template.helper_method_for_template(what) in here. 
  # This can get messy when you are making your helpers available to your
  # views AND use them here. So why not just write the code in here where it belongs
  # and leave helpers to the views? 
end

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