Rails association - difficulty getting form_for to work

I have a Member model that belongs to User

class Member < ActiveRecord::Base

    attr_accessible :name
    belongs_to :user

end


class User < ActiveRecord::Base

    attr_accessible :name
    has_many :members, :dependent => :destroy

end

In my Members controller I have

class MembersController < ApplicationController

  def create
    @user = User.find(params[:user_id])
    @member  = @user.members.开发者_Python百科build(params[:member])
    if @member.save
      flash[:success] = "Member created!"
      redirect_to root_path
    else
      render 'pages/home'
    end
  end
end

In /app/views/users/show.html.erb I have

<%= form_for @member do |f| %>

  <div class="field">
    <%= f.text_area :name %>
  </div>
  <div class="actions">
    <%= f.submit "Submit" %>
  </div>
<% end %>

But I get the following error: undefined method `model_name' for NilClass:Class

Extracted source (around line #18):

15: 
16: <h1 class="member">What's up?</h1>
17: 
18: <%= form_for @member do |f| %>

My show action in the Users controller is

  def show
      @user = User.find(params[:id])
      @members = Member.new
      @title = @user.name
  end

Which also contains the 'new' method

I have tried changing :user_id to :id in the MembersController but this does not work either. What am I doing wrong here?

thanks in advance

Try to replace @members = Member.new by @member = Member.new ;-) !

I needed to pass the @user.id as a hidden field in the form, for the association to work!