连接路线，视图和控制器（导轨）

Question

I'm learning Rails so please pardon my amateur mistakes, but I've been stuck for about an hour or two and have made negative progress.

Goal:

From the user profile view, link to a form that allows this user to change their email. Once the form is submitted, it should trigger an appropriate method within the user controller .

I can handle the rest, I just haven't managed to connect the parts mentioned above. I have been reading railsTutorial.org and guides.rubyonrails.org but haven't been able to understand routing form_for() sufficiently.

User Profile Link:

<%= @user.email %> <%= link_to "(change)", email_path(@user) %>

Routes

Rails.application.routes.draw do
  get    'email'    => 'users#email_form'
  post   'email'    => 'users#changeemail'
end

User Controller

class UsersController < ApplicationController
  def email_form
    @user = User.find(params[:id])
  end

  def changeemail
    @user = User.find(params[:id])
    redirect_to @user
  end
end

Currently the error I get once I click the link is Couldn't find User with 'id'= which I assume means user ID is nil because I fail at passing it.

I would greatly appreciate an explanation of what data is being passed through this workflow so I can be a better developer, thank you very much!

EDIT:

The form itself:

<%= form_for(@user, url: user_path(@user))  do |f| %>
  <%= render 'shared/error_messages' %>

  <%= f.label :new_email %>
  <%= f.text_field :new_email, class: 'form-control' %>

  <%= f.label :password %>
  <%= f.password_field :password, class: 'form-control' %>

  <%= f.submit "Submit New Email", class: "btn btn-primary" %>
<% end %>

Answer 1

You could do this (note :id and "as"):

Rails.application.routes.draw do
  get    'email/:id'    => 'users#email_form', as :email
  post   'email/:id'    => 'users#changeemail', as :change_email
end

The :id is then expected to be part of the route.

Alternatively, pass the id directly when generating the url:

<%= @user.email %> <%= link_to "(change)", email_path(id: @user) %>

---

This will make a call to "UsersController#update"

<%= form_for(@user, url: user_path(@user))  do |f| %>

...instead you would use something like::

<%= form_for(@user, url: change_email_path(@user), method: :put)  do |f| %>

http://api.rubyonrails.org/classes/ActionView/Helpers/FormHelper.html#method-i-form_for

---

...but in terms of best practices, if you want to do separate flow for email updating, you could be more explicit in treating it as a different resource (even though it's still the user record).

For example, you could map these to an explicit 'resource' with a #show and #update action...

Routes:

resources :user_emails, only: [:show, :update]

Controller:

class UserEmailsController < ApplicationController
  def show
    @user = User.find(params[:id])
  end

  def update
    @user = User.find(params[:id])
    redirect_to @user # goes back to UsersController#show
  end
end

Then the route would be:

<%= @user.email %> <%= link_to "(change)", user_email_path(@user) %>

In this case we don't have to say (id: @user) since the 'resource' generates the right urls for you.

...and this would be

<%= form_for(@user, url: user_email_path(@user), method: :post)  do |f| %>