Passing @Object into a Rails Partial Render

Passing @object into a rails partial render

Why is it so important that you use an instance variable(variables who's names begin with '@', eg: @object) in your partial? It's not a good habit to get into. Using instance variables in partials complicates the control flow, which facilitates bugs and makes reuse of partials more difficult. This blog post explains the problem a little more in depth.

Really you have two options. The first option is the suggested solution.

1. Change all instance variables to a local variable and pass it to the partial with the locals argument of render.

2. Set the instance variable before the partial is rendered. Partials have access to all the instance variables that your controller sets.

Again instance variables in partials are bad. You should never set instance variables just because your partials are already written to use them. Rewrite the partial instead.

render partial :object vs :locals

In the second case using :object will define a variable with the same name as the partial by default. If my partial template is named _user.html.erb then there will be a local variable named "user" defined in the template.

You can specify a different variable name with :as => "another_name".

This is documented here:
http://api.rubyonrails.org/classes/ActionView/PartialRenderer.html , here: http://apidock.com/rails/ActionView/PartialRenderer

...and for older Rails (version <= v3.09):
http://apidock.com/rails/ActionView/Partials

Rails pass array to partial using collection

I am not very familiar with the slim-lang, but I think adding the :as option will work for you:

== render partial: "layouts/display_elements", collection: my_array, as: :display_element

This will allow you to access the collection my_array as the display_item local variable within your partial.

Rails 4 Passing multiple variables through render partial

I figured out what the problem is.

I have

<%= f.fields_for :materials do |builder| %>
  <%= render partial: 'material_fields', locals: {f: builder, feed: true } %>
<% end %>

and later in the same view I have

<%= f.fields_for :materials do |builder| %>
    <%= render 'material_fields', f: builder %>
<% end %>

Apparently when rendering the same partial twice from one file the params are messed up. Further testing could isolate the issue but I have not the energy or time.

Solution: Declare the same params on both renders. The values can be different and they work as expected.

<%= f.fields_for :materials do |builder| %>
    <%= render partial: 'material_fields', locals: {f: builder, feed: true } %>
<% end %>

<%= f.fields_for :materials do |builder| %>
  <%= render partial: 'material_fields', locals: {f: builder, feed: false } %>
<% end %>

Render @object and locals vs render :partial

<%= render @products %>

Is indeed the shorthand syntax for rendering a partial. But with the shorthand syntax, Rails will ignore the ":locals" variable. There's more on this in the Rails Guides.

So if you want to pass extra options to the render, you have to specify ":partial => ...". If you want to know why this happens, you can take a look at the Rails source.

Render partials inside loop in Rails 5

Try this code:

#videos.tab-pane.fade.in.active .row - 

@videos.each do |video| 

  = render 'shared/product', product: video 

#articles.tab-pane.fade .row -       

@articles.each do |article| 

 = render 'shared/product', product: article

Error when rendering a partial (RoR) passing the form as a local variable

That's weird. It should work as you have it with :form or :f. If you're using Ruby 1.9, maybe there's some difference in how local variables work. I would try :locals => { "f" => f } with a string key instead of symbol and see if that helps. Also, does it work to use a simpler case like :locals => { :x => 2 }?

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