I have a form displaying a nested relationship. The call to render the nested child objects is made like below:
<% if #fpimgblocks %>
<% f.fields_for #fpimgblocks do |builder| %>
<%= render 'fpimgblock_fields', :f => builder %>
<% end %>
<% end %>
#fpimgblocks is the result of a find, I have verified there are zero results so I expect this to not render. However, the partial is rendered even through the object is not initialized. This then returns a nil_class error when I commit the form.
Is the syntax in the if statement wrong or something? I've tried changing to "unless #fpimgblocks.nil? but no change.
#fpimgblocks is not nil as you're expecting. Since it's the result of a find, it's actually an empty array. Change this:
<% if #fpimgblocks %>
to this:
<% unless #fpimgblocks.empty? %>
And it will work. I hope this helps!
Related
I'm trying to check a value (:cat) form a nested input. If this value is one, display something, else dispay nothing
<%= f.simple_fields_for :elements do |element| %>
<%- if element.cat == 1 %>
<%= render 'elements/element_fields', f: element %>
<% end %>
<% end %>
I tried that, but is not working. I have the error (undefined method `cat'). Do you have an idea to solve that ?
Ask not form object but original one
if element.object.cat == 1
I am new to caching and I'm not sure what my best course of action is.
I want to cache a part of my view that relies on a complex query. The query looks something like:
#sessions_next_week = group_by_wday(LittleClassSession.location_only([1,2]).age_range_only(age_from, age_to).supports_dropins_only(support).approved_users_only.next_week)
Above you'll see a number of scopes and methods called. The view renders an instance variable named #sessions_next_week like so:
<% #sessions_next_week.each do |wday, lcs| %>
<h3><%= wday %></h3>
<%= render partial: 'table_head' %>
<% lcs.each do |s| %>
<%= render partial: 'table_row', :locals => {:s => s, :show_day => true} %>
<% end %>
<%= render partial: 'table_foot' %>
<% end %>
As you can see, #sessions_next_week is iterated through, and its children are iterated through. Given this, and given the nature of the query results in the instance variable, I'm not sure where to implement the caching. In the model? In the view?
So my questions are:
Do I need model caching or can I do this in the view?
What's the correct implementation?
The solution is to simply add two character:
#sessions_next_week ||= group_by_wday(LittleClassSession.location_only([1,2]).age_range_only(age_from, age_to).supports_dropins_only(support).approved_users_only.next_week)
This is called memoization, and you can look it up. Here's one source: http://www.justinweiss.com/articles/4-simple-memoization-patterns-in-ruby-and-one-gem/
I'm trying to experiment with blocks and how to iterate over collections in ERB. I have a models in a one-to-many relatinship (Channel and their corresponding types).
controller
class HomePageController < ActionController
def index
#channels = Channel.all
end
end
Then in the view, I iterate over all the attributes belonging to a Channel. When I want to print all types, this code gives me the desired output:
view
<% #channels.each do |channel| %>
<% #types.each do |type| %>
<%= Type.find(type).name %>
<% end %>
<% end %>
At first I tried to achieve this by using the yield keyword in a neat one-liner but I couldn't manage to print anything to the browser, only to the console
<% #types.each {|type| yield Type.find(type).name } %>
Is there an equivalent one-liner?
First of all this method is so inefficient, you are doing n-queries, to find each record of type Type instead convert those into an array of types by using a single query in the controller, assume that that array is in type_ids
# controller
#channels = Channel.includes(:types) # avoiding n+1 queries
# view
<% #channels.each do |channel| %>
# some channel info output
<% channel.types.each do |type| %>
<%= type.name %>
<% end %> # types loop
<% end %> # channel loop
As #Almaron mentioned, you could render a partial for more simplification, if you have a partial called _type.html.erb you can call render directly
# view
<%= render channel.types %>
Rails will do all the iterating and rendering.
First of all, this kind of code does not belong to the view. Don't tackle the database from the view (in your case Type.find()). Move it to the controller where it belongs.
The second thing to note is the difference between <%= and <% tags. The first one outputs the returned result, while the second one doesn't. The problem with .each is that it returns the object it has been used on, so in your case if you just go <%= #types.each {|type| Type.find(type).name } %> you'll get the #types array printed out.
If you want to simplify that code, you can use a helper method for iterating and a partial for rendering each item. That way you get something like this
<% collection_iterate #items, 'item_partial' %>
I have a main page that is responsible for HTML/CSS styling, but some of the contents come from partials. A partial receives some locals or params, i.e. current_user or person, and displays information if any.
Is there a way for me to check if a partial rendered anything? My end goal is something like this:
<% if my_partial can render something %>
<div class="css_for_something">
<%= render(partial: 'my_partial', locals: {...} ) %>
<% else %>
<div class="css_for_no_info">
<%= render something else %>
<% end %>
I do not want the partials to handle styling logic; they just need to display content if any. Conversely, the main page should not know anything about the logic in the partial(s), such as checking values or querying the database.
Thank you
Unfortunately, Chris Peter's solution did not work for me on rails 4.2.4, as render_to_string seems to not be available in views.
However, the following worked (rails 4.2.4):
<% partial_content = render partial: 'my_partial' %>
<% if partial_content.present? %>
<%= partial_content %>
<% else %>
<%# rendered if partial is empty %>
<% end %>
Be aware that the present? check really only checks if what was rendered is empty. If, something, e.g. a HTML comment, is returned, the check returns false.
Try storing the value generated by render_to_string in a variable:
<% partial_content = render_to_string(partial: 'my_partial', locals: {...} ).strip %>
Then you can see if it contains any content:
<% if partial_content.present? %>
<%= partial_content %>
<% else %>
<div class="css_for_no_info">
<%= render something else %>
</div>
<% end %>
I'm writing some Rails code for a partial view, and I want it to only show a comment field if somebody is already logged onto a site here.
If the page is viewed by someone who isn't a member of the site yet, the shared/comment_not_logged_in fragment should be passed in.
However, I'm totally stumped as to why I can't run the same check to decide if the page should add the class attribute "missing_your_voice" to the enclosing div element here:
<li class="user_submission_form bubble comment_form <% "missing_your_voice" if not current_user %>">
<% if current_user %>
<%= image_tag(current_user.avatar(:comment), :class => "profile_pic") %>
<% form_for [parent, Comment.new] do |f| %>
<%= render "comments/form", :f => f %>
<% end %>
<% else %>
<%= render :partial => 'shared/comment_not_logged_in' %>
<% end %>
</li>
The same idiom, "missing_your_voice" if not current_user returns the string in irb, and also in the console debugger.
What am I doing wrong here?
You forgot an =. Replace <% by <%=, so that you get:
<%= "missing_your_voice" if not current_user %>
Remember that <% ... %> will only run Ruby code, but not display anything. Using <%= ... %> will run the code and display the result of the expression.
As molf already pointed out, there's a missing = on your view.
It should be <%=.
Other than that, be sure to make your controller method available to your view by calling helper_method in your controller.
Take a look on the documentation if needed.