Scope of each on rails template - ruby-on-rails

I'm new to rails and I'm trying to build a view that will list the parents and related children
Ex:
Passport has many Visas
I want to list information about the passport and the visas that the passport has.
So I have
<% #passport_list.each do |passport| %>
# passportFields
<% passport.visas.each do |visa| %>
<%= t.text_field :visa_type %>
<% end %>
<% end %>
I'm getting the error
undefined method `visa_type' for #Passport:0x000000091b8b28
It looks like rails is trying to find the property visa_type for passport, instead of in visa. How does the scope work within each? Can I force it to access visa_type from visa?

I think you're looking for the fields_for form helper. This will allow you to create fields for the relevant visa attributes. Replace your code sample with the following, and you should be all set.
<% #passport_list.each do |passport| %>
# passportFields
<% t.fields_for :visas do |visa_fields| %>
<%= visa_fields.text_field :visa_type %>
<% end %>
<% end %>
You can also iterate over the list as follows:
<% #passport_list.each do |passport| %>
# passportFields
<% passport.visas.each do |visa| %>
<% t.fields_for :visas do |visa_fields| %>
<%= visa_fields.text_field :visa_type %>
<% end %>
<% end %>
<% end %>
For more information on fields_for, check out the link I added above, and to customize further for your use case, check out the "One-to-many" section.

IMO you should always handle the null case of an object.
Something like this if you use rails (present? is a Rails function)...
<% if #passport_list.present? %>
<% #passport_list.each do |passport| %>
passportFields
<% passport.visas.each do |visa| %>
<%= t.text_field :visa_type %>
<%end%>
<%end%>
<% else %>
<p>Nothing to see here</p>
<% end %>
However if your #passport_list is backed by an ActiveRecord Query, you can handle this in the model/helper/controller by returning the .none query on the model. Note that this differs from an empty array because it is an ActiveRecord Scope, so you can chain AR queries onto it
# scope on AR model
def self.awesomeville
where(country_of_origin: "awesomeville")
end
# method queried in controller
#passport_list = Passport.all
if #passport_list.present?
#passport_list
else
Passport.none
end
# additional filtering in view is now possible without fear of NoMethodError
#passport_list.awesomeville
Whereas a ruby Array would raise an error as it would respond to the Array methods.

Related

Rails attribute on manual array

In my controller I have:
#payment_types = [['Cash' ,'1'], ['Card', '2']]
What I'm trying to achieve is to show in view Cash and Card while writing on database 1 and 2.
In my view I tried:
<% payment_types.each do |payment_type| %>
<%= payment_type %>
<% end %>
which shows ['Cash' ,'1'] ['Card', '2']]
How can I show instead in my view Cash or Card?
I'm not sure if I understand your question, but if you want to show only 'Cash', and 'Card', you can do it by passing another argument (responsible for hash value, I called it _ because it's a convention for unused arguments) to your block, like this:
<% payment_types.each do |payment_type, _| %>
<%= payment_type %>
<% end %>
You could also do it like this
<% payment_types.each do |payment_type| %>
<%= payment_type.first %>
<% end %>

Rails how to make conditional inside iteration?

i'm trying to use a conditional inside a iteration but did not worked so, here the scenario:
in this case if the if the order or the product is present should just show the order and products with the feedback.
but even if is present show the feedback with odata and pdata.
someone know why?
<% #feedbacks.each do |feedback| %>
<% if order.present? && product.present? %>
<% order = feedback.order %>
<% product = order.product %>
<% else %>
<% odata = feedback.odata %>
<% pdata = odata.pdata %>
<% end %>
I guess this is what you are trying to do,
<% #feedbacks.each do |feedback| %>
<% if (order = feedback.order).present? && (product = feedback.product).present? %>
<%= order.title %>
<%= product.title %>
<% else %>
<%= (odata = feedback.odata).name %>
<%= odata.pdata.name %>
<% end %>
<% end %>
Note: title and name are assumed columns, replace it with your required/respected attribute.
Please go through this to understand the difference between various erb tags.
Comparison:
for the if condition you are trying to call order and product directly, which will throw error as they are related to feedback.
<% %> just executes the ruby code, you wanted to print the data so need to use <%= %>.
no need to save them in variable when you are not going to use it. I have saved them while checking the existence of the object in the condition and could use to display without querying the db.

Find all entities in database and show them if they exist, gives error: no block given yield

How to make this code work?
<%= articles= Article.find_each
if articles
a.each do |a| %>
****some html****
<% end %>
<% end %>
right now it gives me an error:
no block given (yield)
It's hard to tell because your code is such a mess but i think you are trying to do this:
<% Article.all.each do |article| %>
<!-- some html - reference the local variable `article` in here, inside erb tags, eg -->
<div>
<%= article.name %>
</div>
<% end %>
EDIT: the above code will work fine (by which i mean happily generate no html at all) if there are no Article records in the db. Sometimes in this situation you might want to display some sort of extra info, like "You haven't created any Articles yet" or something. if this is the case you could do something like this:
<!-- typically this variable would be defined in the controller -->
<% #articles = Article.all %>
<% if #articles.blank? %>
<p>You haven't created any Articles yet</p>
<% else %>
<% Article.all.each do |article| %>
<!-- some html - reference the local variable `article` in here, inside erb tags, eg -->
<div>
<%= article.name %>
</div>
<% end %>
<% end %>

Conditional line spacing in ERb partials

This is the code for an address partial I just wrote. People might put single line addresses in either street line, company name is optional, etc... It works exactly how I want it to, but I know that checking each variable twice is ugly and terrible.
<%= "#{a.name}" unless a.name.blank? %>
<% unless a.name.blank? %> <br> <% end %>
<%= "#{a.company_name}" unless a.company_name.blank? %>
<% unless a.company_name.blank? %> <br> <% end %>
<%= "#{a.street_1}" unless a.street_1.blank? %>
<% unless a.street_1.blank? %> <br> <% end %>
<%= "#{a.street_2}" unless a.street_2.blank? %>
<% unless a.street_2.blank? %> <br> <% end %>
<%= "#{a.city}, #{a.state} #{a.zip}" %>
So, my gratuitous use of unless aside, how should I be putting in a conditional line break?
Update:
As discussed below, it is dangerous to use .html_safe on user input. If you do use a helper method as suggested below, you must also sanitize all user input on the way into the database. I've rewritten the code above as:
<% unless a.name.blank? %>
<%= a.name %>
<br>
<% end %>
<% unless a.company_name.blank? %>
<%= a.company_name %>
<br>
<% end %>
<% unless a.street_1.blank? %>
<%= a.street_1 %>
<br>
<% end %>
<% unless a.street_2.blank? %>
<%= a.street_2 %>
<br>
<% end %>
<%= "#{a.city}, #{a.state}" %> <%= a.zip %>
The redundant checking was just me overcomplicating things. I'd strongly recommend against using .html_safe in a situation like this, since you create new problems for yourself: sanitizing the input, and remembering which fields are safe. Better to not override the sensible protection Rails provides.
There are many, many ways to go about cleaning it up, but a helper would be appropriate here:
module ApplicationHelper
def format_address(a)
top = [a.name, a.company_name, a.street_1, a.street_2]
top.reject! {|s| s.blank?} # remove null and empty values
"#{top.join('<br/>')}#{a.city}, #{a.state} #{a.zip}".html_safe
end
end
Then in your view:
<%= format_address(a) %>

Rails .each except if

I have a rails table called Movies. Movies are being collected and saved from an API which means that some movies may have a release_date and some may not.
All Movies are being displayed on the home page and they are sorted by {|t| - t.release_date.strftime("%Y%m%d").to_i}
<% #movies.sort_by{|t| - t.release_date.strftime("%Y%m%d").to_i}.each do |movie| %>
<% movie.title %>
<% movie.release_date.strftime("%Y") %>
<% end %>
So this code works fine but only as long as the returned movies have a release date. If they don't have a release date assigned, it gives me the following error.
ActionView::Template::Error (undefined method `strftime' for nil:NilClass):
But im only getting this error if the movie has no release_date.
So how can i add an exception to only display films WITH a release_date, where using strftime would no longer be a problem.
I've tried
<% unless movie.release_date.blank? %>
<% #movies.sort_by{|t| - t.release_date.strftime("%Y%m%d").to_i}.each do |movie| %>
<% #movie.title %>
<% #movie.release_date.strftime("%Y") %>
<% end %>
<% end %>
But that doesn't work as it gives an undefined method for 'movie'
You should be able to use reject to reject nil release_date like follows:
<% #movies.reject{ |m| m.release_date.nil? } %>
Another problem is you are using the variable movie as instance variable #movie within your each block.
Try:
<% #movies.reject{ |m| m.release_date.nil? }.sort_by{|t| - t.release_date.strftime("%Y%m%d").to_i}.each do |movie| %>
<% movie.title %>
<% movie.release_date.strftime("%Y") %>
<% end %>
Update:
And yes, as pointed by #NicolasGarnil in his answer, it's better to do these in SQL side than in ruby side. Select only the required records and let database do the sorting. So you could update your code to be something like:
In controller:
#movies = Movie.where('release_date is not null').order('release_date desc');
Then in your view:
<% #movies.each do |movie| %>
<% movie.title %>
<% movie.release_date.strftime("%Y") %>
<% end %>
For performance reasons you should not be using ruby to sort your records. This should be done at a database level.
You should first ensure that the release_date values are persisted in an appropriate format and then just use Movie.order("release_date desc"). Records with null values will be placed at the end of the results.

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