从视图Ruby on rails调用控制器方法

Question

I am very new to ruby. I have one doubt, how to call a controller method from a view.

my controller

def course_user_count
 @courses=Course.all
 @courses.each do |course|
 @count=course.students.count
end

I have to call this @count variable from the method in my view course.view.html.erb

Answer 1

At the top of your controller you can mark the method that you want available to your views as a helper method:

helper_method :course_user_count

Then in your view, you can call course_user_count and store the result.

<% count = course_user_count %>

Answer 2

I don't quite understand what you mean when you say that you have to "call this @count variable" from your view. Are you not setting that variable in your controller? If so, it should automatically be accessible in the associated view. (You don't "call" a variable, you read it or set it.)

Second, your method reads each course's student count and then assigns it to the variable @count . Each time this variable is written to, its previous value is overwritten, so the method as written is useless. I'm not sure what you're trying to do here -- perhaps "initializing" the controller by setting this value in advance for each course?

By convention, a controller's show method shows the information for one line of the associated database. If the aim is to show the course's student count in that view, I would write something like this in app/controllers/course_controller.rb :

class CourseController < ApplicationController

  def show
    @course = Course.find(params[:id]) # Here I assume that the url is .../courses/<id>
    @student_count = @course.students.count
  end

  ...

end

And display the variable's value like this in template app/views/courses/show.html.erb :

<%= @student_count %>

In other words, I wouldn't write a method in the controller to return a course's student count, but instead just pass it as a parameter to the view, just as I would pass anything else the view needs to display -- or at least anything that the view can't access by a very simple operation, a condition not really fulfilled by @course.students.count , but that's a matter of taste.

However, it might make sense to define a method in the controller for values that are more complex to compute and/or are not needed every time the show template is displayed. To make that method callable from your views, the method has to be declared a helper method, as Keith mentioned in his answer. For instance, a method that returns the total student count of all courses in app/controllers/course_controller.rb :

class CourseController < ApplicationController

  helper_method :total_student_count

  def total_student_count
    total_count = 0
    Course.all.each do |c|
      total_count += c.students.count
    end
    total_count
  end

  ...

end

Use the method like this in any template under app/views/courses/ to display the value returned by that method:

<%= total_student_count %>

Answer 3

declare method name as the helper method

In the view call the method as

<% count = course_user_count %>

Answer 4

Your controller is accessible in your view through the variable:

@controller

which is available by default. I'm talking about the controller associated with that particular view of course.

In your case:

@controller.course_user_count