Hey guys I have a simple create method with some validations and whenever the create method fails due to validation errors it re-renders the 'new' action.
The problem is in my new action/view I have a local variable that is established in the action and passed to a partial to render some related information to what the user is creating.
Now when my create action fails and I try to re-render the 'new' action I'm getting the always awesome
undefined method `cover' for nil:NilClass
error.
What is the best way to handle re-establishing my action's local variables on a render instead of redirecting to the action again and the user losing the data they input?
For some clarification. Here is some sample code:
#controller.rb
def new
#summary = User.find(params[:user_id])
#page = Page.new
end
def create
#page = Page.new(params[:page])
if #page.save
redirect_to #page
else
render :action => 'new'
end
end
in my new.html.erb file i have something like this
<%= #summary.cover %>
#page form etc...
When you create the object and attempt to save it, the object still holds the values and the validation errors, so pass it on into the render. Usually it is named the same in your create method as it is in your new method, so the template just works.
if #my_object.save
flash[:notice] = "Successfully created."
redirect_to ....
else
render :action => 'new' #assuming new.html.erb uses #my_object
end
Related
New web developer here, and I think I may be missing some very fundamental knowledge.
Given the code
def create
#post = Post.new(post_params)
if #post.save
redirect_to #post
else
render "new"
end
end
why does the view templates redirect to the def show action? If I do not define a def show and its corresponding views, rails will throw me an error.
I am just not understanding why even though the code is redirect_to #post after I save a post, it appears to be redirecting to the show page after creating a post. Is this just one of those rails thing that I should just take it as it is or am I missing some fundamental HTML protocol knowledge (which I honestly don't know a lot about)?
Edit: To further clarify my question, I see that #post is already defined in the create method and is defined as Post.new(post_params). when I redirect_to #post, wouldn't it simply call that line again?
Lets take a look at your code
def create
#post = Post.new(post_params)
if #post.save
redirect_to #post
else
render "new"
end
end
why does the view templates redirect to the def show action? If I do not define a def show and its corresponding views, rails will throw me an error.
In create action you are creating a new record, so if you look at this part of the code
if #post.save
redirect_to #post
When #post is successfully saved, we are redirecting it to show action by writing redirect_to #post, the actual route for show action would be post_path(#post) so you can also write redirect_to post_path(#post) but even if you simply pass object with redirect_to rails will redirect it to the show action. Now going to the else part
else
render "new"
If the #post object is not saved in the database(due to validation), we want to reload the form, so in the above code render is just rendering the view of new action and not calling the new action, only the view is rendered because new.html.erb contains the form.
Hope this helped!
Let's say I create a scaffold:
rails g scaffold Cat name:string age:integer
and I add a presence validation on the Cat model's age attribute:
validates :age, presence: true
When I attempt to create a cat via the form, and put in the cat's name but purposely leave out the cat's age the controller bounces me back to the form but that cat's name is still present in the name field!
How is this happening?
I would have thought the
#cat = Cat.new
would replace all of the invalid cat's attributes. Maybe if it were #cat ||= Cat.new I could understand that more.
Also, how can I make this behaviour happen in a more complex rails app? I have a simple forum where topics has_many replies. I create my new replies via a form in my topic show view:
topic#show:
#reply = Reply.new
topic/show.html.erb:
<%= form_for [#toplic, #reply] do |f| %>
<%= f.text_field :name placeholder: 'Create a new name...' %><br>
<%= f.text_area :description, placeholder: 'Create a new description...', rows: 5 %><br>
<%= f.submit 'Create Discussion' %>
<% end %>
While everything works perfectly, when I purposely leave out a reply's name, though I am redirected back to the form and an error flash shows, my form is completely empty. All of the attributes have vanished? Why is this?
The key to understanding how this works is to realize that in the case of a form failure, the controller action is not rerun, but rather the template is rendered using the existing state from the action.
In a typical Rails scaffold, your create action will look like this
def create
#cat = Cat.new(cat_params) # instance variable is initialized with the form values
if #cat.save
redirect_to #cat, notice: 'Success!'
else
# in the case of form failure, we will re-render the 'new' template
# this will NOT rerun the entire 'new' action, thus the #cat variable
# will still maintain the values from the form that we gave it above
render 'new'
# note the difference if we had instead done a redirect_to; this would
# cause the CatsController#new action to be re-run which would reinitialize
# the #cat variable according to the code within the 'new' action
# redirect_to new_cat_url
end
end
For your more complex example, you'll want to follow the same procedure, making sure you just re-render the form and don't redirect to another action (which will cause the state to be lost).
# TopicsController
def show
#topic = Topic.find(params[:id])
#reply = Reply.new
end
# RepliesController
def create
#reply = Reply.new(reply_params) # init the var with the form values
if #reply.save
redirect_to #topic, notice: 'Success!'
else
# this is the key - we need to re-render the template of the previous action
# in this case, it would be the TopicsController#show template
render 'topics/show'
# Remember - if we instead do a redirect_to #topic, then we will lose the form
# values which are currently set in the #reply variable.
end
end
In short, make sure you recognize when you are redirecting to a new action versus just re-rendering a template.
One important GOTCHA to be aware of when re-rendering a template is that you must make sure that all the instance variables which exist for the controller action are available when you render the template.
For example,
# TopicsController
def show
#topic = Topic.find(params[:id])
#reply = Reply.new
#foo = Foo.new
end
# RepliesController
before_action :set_topic
def create
#reply = Reply.new(reply_params)
if #reply.save
# ...
else
# we need to remember to set up a #foo variable here otherwise it will be undefined
# when used within the 'show' template
#foo = Foo.new
render 'topics/show'
end
protected
def set_topic
#topic = Topic.find(params[:topic_id])
end
OK, so, you go go /cat/new. Rails' route for this URL runs the method CatsController#new, which renders the new.html.erb template. You put in your data, then hit submit. The action for this form is to POST to /cats, which runs the CatsController#create method. This method does this following:
#cat = Cat.new(cat_params)
It then tries to save the Cat. If it succeeds, it redirects you to the Cat's URL. If not, it re-renders the new.html.erb template. That's where the name comes from — the CatsController#update method creates its Cat from the values you put into the original form.
For a typical scaffold create action:
# POST /products
# POST /products.json
def create
#product = Product.new(params[:product])
respond_to do |format|
if #product.save
format.html { redirect_to #product, notice: 'Product was successfully created.' }
format.json { render json: #product, status: :created, location: #product }
else
format.html { render action: "new" } #will re-submit
format.json { render json: #product.errors, status: :unprocessable_entity }
end
end
end
The magic happens in the render method! which will submit the previous POST request (won't go back to the new action while a redirect will do), this way the submited values are still there. (check this SO question for more details)
That's said, this behavior relies on following the convention, however sometimes you need to give it a hand specially with some inputs (e.g selects, checkboxes, radio) might require extra setup using selected or value options
I have a helper which instantiates a model and renders a form. This form should be available to any view in the application
# support_form_helper
def support_form
#support_stats = SupportForm::Stat.find(get_stats_id)
#enquiry = SupportForm::Enquiry.new(stats_id: #support_stats.id)
render partial: 'support_form/enquiries/form'
end
And its rendered in the view:
# some_view.html.erb
<%= support_form %>
This is fine until I want to submit the form and validate it in the controller.
# enquiries_controller.rb
def create
#enquiry = SupportForm::Enquiry.new(params[:support_form_enquiry])
topic = #enquiry.topic
#stat = SupportForm::Stat.find(#enquiry.stats_id)
#stat.stats[topic] = #stat.stats[topic].to_i.next
respond_to do |format|
if #enquiry.valid? && #stat.save
format.html { redirect_to(root_path) }
else
format.html { redirect_to(:back) }
end
end
end
This is where I can't render the previous view with the errors attached to the invalid object. The helper gets invoked again and initializes a new #enquiries object, without the errors obviously.
How can I render the form in many views across an application and still return to the view with the object together with errors when it is invalid?
I found an answer which answers my question but its a bad idea:
Render the action that initiated update
def create
#enquiry = SupportForm::Enquiry.new(params[:support_form_enquiry])
topic = #enquiry.topic
#stat = SupportForm::Stat.find(#enquiry.stats_id)
#stat.stats[topic] = #stat.stats[topic].to_i.next
if #enquiry.valid? && #stat.save
redirect_to(root_path)
else
render Rails.application.routes.recognize_path(request.referer).values.join("/")
end
end
The problem is that there will likely be instance variables in the view that submitted the form and I would have to be able to instantiate all the instance variable in the application then.....not possible.
Currently I'm considering putting the errors in the flash hash... not something I want to do. With the original object returned i can repopulate the fields with the users input.
When you use redirect_to, rails will kick off a whole new controller & view sequence. Use
render "path/to/template/from/view/folder"`
instead.
A typical create action using this pattern would look like (for a 'post' object in this case):
def create
#post = Post.new(params[:post])
#created = #post.save
respond_to do |format|
if #created
flash[:notice] = 'Post was successfully created.'
format.html { redirect_to post_path(#post) }
format.js
else
format.html { render :action => :new }
format.js
end
end
end
Notice how if it's successfully created we do a full redirect to the "show" page for the post, but if it's not successful we just do a render.
You should probably modify your support_form helper so that it only creates a new #enquiry if it hasn't been created already:
def support_form
#support_stats = SupportForm::Stat.find(get_stats_id)
#enquiry ||= SupportForm::Enquiry.new(stats_id: #support_stats.id)
render partial: 'support_form/enquiries/form'
end
||= is shorthand for "equals itself or". If it hasn't been defined (or is nil or false) then it will fail the first part of the or and pass through to the second, where the object is created.
In your form partial, also, you should make sure you're using form_for, which will submit to the create or update action depending on whether the object has been saved already.
I have a form for creating a ticket, which needs an id of a project. This works but not when it comes to validation. If validation won't pass 'render :new' is executed and the project_id doesn't come with it.
I have tried 'redirect_to new_ticket_path(:project_id => params[:ticket][:project_id]) which renders the form again, but the error messages won't show up so it seems that I need to use 'render :new'.
How can I pass the project_id back to the form or reach project_id from the form without passing it?
def new
#ticket = Ticket.new
#id = params[:project_id]
#project = Project.find(#id)
end
def create
#ticket = Ticket.new(params[:ticket].merge(:user_id => current_user.id))
if #ticket.save
redirect_to #ticket
else
render :new <--- will render without the project_id
end
end
That will render just the view for 'new', but will not run the controller action. You'd need to set up your variables for the 'new' view in your 'create' action.
From http://guides.rubyonrails.org/layouts_and_rendering.html#using-render
Using render with :action is a frequent source of confusion for Rails
newcomers. The specified action is used to determine which view to
render, but Rails does not run any of the code for that action in the
controller. Any instance variables that you require in the view must
be set up in the current action before calling render.
The easiest way around this is to change 'new':
def new
#ticket = Ticket.new(:project_id => params[:project_id])
end
and change any references to #project in your 'new' form to #ticket.project. At that point, you shouldn't have to add anything to your 'create' action as long as your form includes a hidden field for the ticket's project id.
The easiest way to get this working (and I would do this anyway) is to nest the task resource under projects. That way you will always have project_id available in params.
# config/routes.rb
resources :projects do
resources :tasks
end
The urls will look like projects/123/tasks/new etc. Take a look at rake routes.
Write project id into a hidden field in your form and you will okay. And don't forget to initialize #id in your create action
def new
#ticket = Ticket.new
#id = params[:project_id]
#project = Project.find(#id)
end
def create
#ticket = Ticket.new(params[:ticket].merge(:user_id => current_user.id))
#id = params[:project_id] # but make sure it is under this key in params
if #ticket.save
redirect_to #ticket
else
render :new <--- will render without the project_id
end
end
and in the form add
<%= hidden_field :project_id, '', value: #id %>
Why don't you use:
flash[:alert] = #ticket.errors.inspect
redirect_to new_ticket_path(:project_id => params[:ticket][:project_id])
I have been trying to get to grips with jQuery and been following a railscast on adding an Ajax add review form, which works fine but I would now like to add into it the ability for a review to belong to a user as well as a venue.
Reviews controller
def create
#review = Review.create!(params[:review])
#review.venue = #venue
if #review.save
flash[:notice] = 'Thank you for reviewing this venue!'
respond_to do |format|
format.html { redirect_to venue_path(#venue) }
format.js
end
else
render :action => :new
end
end
views\reviews\create.js.erb
$("#new_review").before('<div id="flash_notice"><%= escape_javascript(flash.delete(:notice)) %></div>');
$("#reviews_count").html("<%= pluralize(#review.venue.reviews.count, 'Review') %>");
$("#reviews").append("<%= escape_javascript(render(:partial => #review)) %>");
$("#new_review")[0].reset();
I have tried changing the controller to:
def create
#review = #current_user.reviews.create!(params[:review])
#review.venue = #venue
if #review.save
flash[:notice] = 'Thank you for reviewing this venue!'
respond_to do |format|
format.html { redirect_to venue_path(#venue) }
format.js
end
else
render :action => :new
end
end
but it just wont submit, with no errors.
I think I have the models set correctly with belongs_to and has_many, I think this is a controller issue I'll add other code bits if needed.
Development log
NoMethodError (undefined method `reviews' for nil:NilClass):
app/controllers/reviews_controller.rb:14:in `create'
Thanks for any help!
It appears that your error is residing with #current_user. According to your development log, #current_user is nil when you call #current_user.reviews on it. I would say track down where this #current_user instance variable is being set and find out why it is nil. Now, what kind of authentication are you using? Most authentication plugins, especially those used by Ryan Bates of the Railscasts you mentioned, use a local variable, say just current_user, as the means to access the currently signed in user. I know I do in all my code.
So, rewrite the line as
#review = current_user.reviews.create!(params[:review])
and see if that works. If it doesn't, change it back and then track down where this #current_user is being set. Chances are good it is being set in a before_filter :method_name at the beginning of your controller.
Calling create! (with exclamation mark) will throw an exception and thus abort your create action if saving fails. Check your log/development.log for these exceptions.
Use build instead of create and lose the exclamation mark.
def create
#review = #current_user.reviews.build(params[:review])
#review.venue = #venue
if #review.save
flash[:notice] = 'Thank you for reviewing this venue!'
respond_to do |format|
format.html { redirect_to venue_path(#venue) }
format.js
end
else
render :action => :new
end
end