Return original selection in collection_select when editing entry

I'm trying to get my head around collection_selects in Rails. I can populate the dropdown from a database table, submit the selected option, and show the result. However I can't figure out how to show the selected option in the dropdown when the开发者_如何学JAVA user chooses to edit the entry.

Here's an extract from my view code:

<p>
  <%= f.label :Status %><br />
  <%= f.text_field :status %>
</p>
<p>
  <%= f.label :Manager %><br />
  <%= f.collection_select(:manager, @managers, :id, :name, {:include_blank => true}) %>
</p>

Here's my controller code:

class ProjectsController < ApplicationController
  # GET /projects
  # GET /projects.xml

  before_filter :require_user

  def index
    @projects = Project.all

    respond_to do |format|
      format.html # index.html.erb
      format.xml  { render :xml => @projects }
    end
  end

  # GET /projects/1
  # GET /projects/1.xml
  def show
    @project = Project.find(params[:id])

    projectid = params[:id]
    @evidence = Evidence.find(:all, :conditions => ["projectid = ?", projectid])

    respond_to do |format|
      format.html # show.html.erb
      format.xml  { render :xml => @project }
    end
  end

  # GET /projects/new
  # GET /projects/new.xml
  def new
    @project = Project.new
    @managers = Manager.find(:all)

    respond_to do |format|
      format.html # new.html.erb
      format.xml  { render :xml => @project }
    end
  end

  # GET /projects/1/edit
  def edit
    @project = Project.find(params[:id])
    @managers = Manager.find(:all)
  end

  # POST /projects
  # POST /projects.xml
  def create
    @project = Project.new(params[:project])

    respond_to do |format|
      if @project.save
        flash[:notice] = 'Project was successfully created.'
        format.html { redirect_to(@project) }
        format.xml  { render :xml => @project, :status => :created, :location => @project }
      else
        format.html { render :action => "new" }
        format.xml  { render :xml => @project.errors, :status => :unprocessable_entity }
      end
    end
  end

  # PUT /projects/1
  # PUT /projects/1.xml
  def update
    @project = Project.find(params[:id])

    respond_to do |format|
      if @project.update_attributes(params[:project])
        flash[:notice] = 'Project was successfully updated.'
        format.html { redirect_to(@project) }
        format.xml  { head :ok }
      else
        format.html { render :action => "edit" }
        format.xml  { render :xml => @project.errors, :status => :unprocessable_entity }
      end
    end
  end

  # DELETE /projects/1
  # DELETE /projects/1.xml
  def destroy
    @project = Project.find(params[:id])
    @project.destroy

    respond_to do |format|
      format.html { redirect_to(projects_url) }
      format.xml  { head :ok }
    end
  end
end

And here's the code for my models:

class Manager < ActiveRecord::Base
    has_many :projects
end

class Project < ActiveRecord::Base
    belongs_to :manager

    validates_presence_of(:name, :reference, :client, :status)
    validates_uniqueness_of (:reference)
end

Any help is greatly appreciated.

Thanks!

---

According to the documentation:

collection_select(object, method, collection, value_method, text_method, options = {}, html_options = {})

...The value returned from calling method on the instance object will be selected.

This means that your :manager method must return a value that matches one of the managers in your @managers instance variable in order for that to be the selected option.

---

I think you need to change :manager to :manager_id:

<%= f.collection_select(:manager_id, @managers, :id, :name, {:include_blank => true}) %>