Okay so in the index portion of my controller I set
#patients = Patient.all
then in patients_helper.rb
def race_abrev
return self.caucasian
end
where caucasian is an integer datatype column in the patients table
then in the view index.html.erb
<% #patients.each do |p| %>
<td><%= p.gender %></td>
<td><%= p.ethnicity %></td>
<td><%= p.race_abrev %></td>
<% end %>
I get a
undefined method `race_abrev' for #<Patient:0xb4d95cd8>
I've checked the table and I'm expecting patient.caucasian to return the integer 1, what am I missing..any insight to a fundamental misunderstanding I seem to have?
race_abrev is a helper, not a method on Patient:
<%= race_abrev(p) %>
And the helper itself would return p.caucasian, although it'd seem like you'd actually want to do something with the value of caucasian, like a compare or something.
All this said, I'm not sure why you're not defining it (or what "it" actually is) on the model, since so far it doesn't seem to have anything to do with the view, which is what view helpers are for.
If you're storing something in the DB you want to transform it may or may not belong in a view helper; if it's to turn it into something human-readable I'd be more likely to put it in the model.
Related
I have a model Schools and a model PerformanceStats.
PerformanceStat
belongs_to :school
School
has_one :performance_stat
the index page for PerformanceStat shows all 2,000 performance stats, and also the school.name, school.score, and school.city, and I need access to the school.id and school.slug.
Controller:
def index
#performance_stats=PerformanceStat.all
end
My view code:
<tbody>
<% #performance_stats.each do |stat| %>
<% school = School.find(stat.school_id)%>
<tr>
<td><%= link_to school.name, school_path(city: school.city.parameterize.truncate(80, omission: ''), slug: school.slug) %></td>
<td><%= number_with_precision(school.score, precision: 2)%></td>
then the view goes on to display the performance stats.
This view load very slowly....10-20 seconds. How can I speed things up? I've tried PerformanceStats.scoped, and plucking school stats and selecting from an array, but these don't seem to help. Is there a way for me to access the school attributes without finding a School for every PerformanceStat? I believe the School.find bit is slowing things down considerably.
I have indexes on :school_id in PerformanceStat, and :score, :slug in the School model.
UPDATE:
The suggestion in the selected answer to add a cache resulted in this line of code in the index action of the SchoolsController:
fresh_when etag: #performance_stats
The load time dropped to 18ms. This solution works great for me because the content of the index action does not change often. This data gets updated once a year. This link has other suggested cache solutions for data that changes frequently.
PerformanceStat.all is a heavy query if you've a lot of data in this table and it'll be finding school for each performance stat.
What I can understand from your code is that you're facing (N + 1) problem over here.
NOTE: you should not fire queries from your views or helpers and let the controller do all the action.
For instance in your code:
<% #performance_stats.each do |stat| %>
<% school = School.find(stat.school_id)%> <- #THIS IS WRONG & LET THE ASSOCIATIONS DO ALL THE ACTION ON ITS OWN
<tr>
<td><%= link_to school.name, school_path(city: school.city.parameterize.truncate(80, omission: ''), slug: school.slug) %></td>
<td><%= number_with_precision(school.score, precision: 2)%></td>
you can use includes, PerformanceStat.includes(:school) it will fetch all the schools for each PerformanceStat.
your controller code should be:
#performance_stats = PerformanceStat.includes(:school)
instead of : #performance_stats = PerformanceStat.all
and your view code will now be:
<% #performance_stats.each do |stat| %>
<% school = stat.school %> #make sure all stats have a school assigned to them otherwise you can put a check below whether the school is nil or not
<tr>
<td><%= link_to school.name, school_path(city: school.city.parameterize.truncate(80, omission: ''), slug: school.slug) %></td>
<td><%= number_with_precision(school.score, precision: 2)%></td>
Quite a few things here. First of all change your controller method to this one, otherwise you will run into n+1 queries
def index
#performance_stats=PerformanceStat.includes(:school)
end
Since you have eagerly loaded the school, now you can access it directly in your view as
<% stat.school %>
Secondly loading almost 2000 records in one go is not optimal at all, it's gonna take a while to load all records. For this you must add pagination by using following gems
kaminari
will_paginate
I have a show page where I need to both show the student's units and create a unit for them. However an error is being incurred when trying to do both.
In my controller
def show
#student = Student.find(params[:id])
#unit = #student.units.build
#units = #student.units
end
In my view
<%= simple_form_for #unit, url: student_units_path(#student) %>
# form...
<% end %>
<% #units.each do |unit| %>
<tr>
<td><%= unit.course %></td>
<td><%= unit.mailing_date.strftime('%m/%d/%y') %></td>
</tr>
<% end %>
The unit.course call works and any call that is only the first child of unit, however when I call a second method on unit I get this error:
undefined method `strftime' for nil:NilClass
despite knowing that the unit exists, hence the first call working
It seems your issue is that unit.mailing_date is nil, for newly-built records.
One solution would be to define a default value for mailing_date, either at the database level or in your application. For example, you could do something like:
class Unit < ActiveRecord::Base
# ....
after_initialize :set_default_mailing_date
private
def set_default_mailing_date
self.mailing_date ||= Date.today
end
end
Or alternatively, you could leave the mailing_date as nil and handle this gracefully in the view:
<td><%= unit.mailing_date.try!(:strftime, '%m/%d/%y') %></td>
If you are using ruby version 2.3+, then I would advise using the built-in safe navigation operator, rather than ActiveSupport's try! method:
<td><%= unit.mailing_date&.strftime('%m/%d/%y') %></td>
Finally, if you went with the above choice to leave the mailing_date as nil, then perhaps you'd like to display some default value in its place - for example:
<td><%= unit.mailing_date&.strftime('%m/%d/%y') || 'Not set' %></td>
As an alternative, I assume you don't want the new unit bound to the form being rendered which is what is causing the error.
You could do
#units = #student.units.reject(&:new_record?)
To remove the newly built unit from the collection
I get that one should not ping the database in the view... but wondering about the right solution. In one of my views, I need to pull info on an #order, it's child items, and also Amount, another model, based on each child item. Something like this:
<% #order.items.each do |item| %>
<td><%= item.name %></td>
<td><%= Refund.where(item_id:item.id).first.amount %></td>
<td><%= Amount.where(item_id: item.id).first.amount %></td>
<% end %>
For the sake of avoiding the db hits in the view, the only solution I've thought of is to create a huge hash of all the relevant data in the controller, which is then accessed from the view. So it would be something like this:
# controller (writing quickly, code may not be totally right, hopefully you get gist
data = Hash.new
data["items"] = []
#order.items.each do |item|
item_hash = {
"name" => item.name,
"amount" => Amount.where(item_id: item.id).first.amount,
"refund" => Refund.where(item_id:item.id).first.amount
}
data["items"] << item_hash
end
# view code
<% data["items"].each do |item| %>
<td><%= item["name"] %></td>
<td><%= item["refund"] %></td>
<td><%= item["amount"] %></td>
<% end %>
And I know SO hates this type of question... but I really need to know... is that the best solution? Or are there are best practices? The reason I ask is because it seems very clean in the view, but very bulky in the controller, and also it gets quite unwieldy when you have a much more complex set of nested tables, which is what I actually have (i.e., the data hash would be quite funky to put together)
First of I would use associations between item and the 2 other classes, so that you can do
item.refund
item.amount
Instead of Refund.where(...). You could further define methods such as
def refund_amount
refund.amount
end
And similarly for the other one (and hopefully come up with a better name than amount_amount.
This keeps both your view and controller clean but it won't be any faster. So far all of the approaches involve running 2 database queries per item which is the real issue as far as I'm concerned - whether those excess queries happen in the view or the controller is of lesser concern.
However you can avoid this with Active Record's include mechanism:
Item.include(:amount,:refund).where("your conditions here")
Will load the named associations in bulk rather than loaded them one at a time as each item is accessed.
I have three models. One is an Employee, one is an Item, and one is a Transaction that belongs to both Employee and Items. It's a simple app that allows Employees to check in and check out items - 'Transaction' has a boolean column for checked-in/checked-out.
What I'm trying to do is show within the employee/show view the current list of Items that an Employee has checked out. This is some rough code that I sketched out, but I'm not sure that it's going to work, and I was told not to use a lot of nested conditionals in my views anyway.
<% if #employee.transactions.exists? %>
<h3>Currently Checked-OUT Items</h3>
<table>
<tr>
<th>Item Asset Tag</th>
<th>Item Description</th>
</tr>
<% #employee.transactions.each do |transaction| %>
<% if item.transaction.last? && transaction.status == false %>
<tr>
<td><% transaction.assettag %></td>
<td><% transaction.description %></td>
</tr>
<% else %>
NO CHECKED OUT ITEMS
<% end %>
</table>
<% end %>
<% end %>
Basically, I'm trying to:
checks all employee transactions
compares the item involved in the transaction and sees if it's the .last transaction record for item
if it is, and if it's false, then it's a current checkout.
Is this a better job for a scope within the Transaction model, or a helper method? I've never used either, I'm really new at rails.
You should do a couple of things in here.
First - create a scope that will fetch last item transaction for you. There's no point in going through al item transactions if you're interested in the last one only, right?
Second, use partials. In this example it's hard to show how I would refactor code to use them (some things doesn't make sense here, ex. where does item variable come from?)
Scope example (take last transaction)
#item.transactions.order('created_at DESC').first
You can as well add scopes for checkin / checkout
class Transaction
scope :checkin, -> { where(status: true) }
scope :checkout, -> { where(status: false) }
end
First, you are on the right track. When views get ugly and hard to read because of extensive embedded ruby conditionals and such, think about moving the logic into a helper.
If you have a typical rails app, you'll already have app/helpers/application_helper.rb
So you could just create a helper in that file
def make_employee_list(employee)
if employee.transactions.exists?
content_tag(:div) do
content_tag(:h3, "Currently Checked-OUT Items")
content_tag(:table) do
employee.transactions.each do |transaction|
# you get the idea
end
end
end
end
end
Then in your view you could do this:
<%= make_employee_list(#employee) %>
Rails 2.3.5
I have a view displaying 'employee' records in a table where each table row haas a check_box_tag to select that (row) employee record (the table is inside a form_tag). The checkbox is passing an array of employee numbers to a method but I also need it to pass some of the other information from the record (first_name, last_name, etc) in the params.
Orignally this looked like (just passing an param with an array of employee numbers)
<% #employee_search.each do |e| %>
<td><%= check_box_tag 'selected_subordinates[]', e.employee_number %></td>
<td><%= e.employee_number %></td>
<td><%= e.first_name %></td>
<td><%= e.last_name %></td>
...
<% end %>
I'm not sure this was right, but I thought I should pass the entire record ('e') in the param:
<% #employee_search.each do |e %>
<td><%= check_box_tag 'selected_subordinates[]', e %></td>
<td><%= e.employee_number %></td>
<td><%= e.first_name %></td>
<td><%= e.last_name %></td>
...
<% end %>
The param array now looks like:
"selected_subordinates"=>["#<Employee:0xa946970>", "#<Employee:0xa946910>", "#<Employee:0xa9468b0>"]
I thought at this point I would be fine and just itterate through the objects in the param array referring to the record fields, but got an undefined method error:
params[:selected_subordinates].each do |s|
puts s.last_name
end
undefined method `last_name' for "#<Employee:0xa946970>":String
I started wondering if for some reason the entire model object was passed instead of just one record from the object. But, trying [0].last_name resulted in a different error.
params[:selected_subordinates].each do |s|
puts s.last_name
end
undefined method `last_name' for 35:Fixnum
Maybe I should have been using the fields I need to build an array for the param - so the param would be an array of arrays? I haven't had any luck so far trying to search for example of what to do when you need to setup a param array made of arrays, or pass a single model object record (and refer to it).
Thank You - Much Appreciated!
When you used e as the param, Rails was converting e to a String and passing that (you can't pass an object in an HTML form, right? Just values). When you saw "#<Employee:0xa946970>" in your params hash, it wasn't an Employee object, but instead a String with the contents of #<Employee:0xa946970> (which is what you get if you called .to_s on an Employee object).
Passing the ID gets you on the right track, but once you have the ID, you should look up the Employee with that ID from the database.
params[:selected_subordinates].each do |s|
employee = Employee.find(s)
puts employee.last_name
end
Of course, this loads them one at a time, so if you have a lot of checkboxes you could end up generating a large number of queries. You can also use the find method to find multiple objects based on an array of IDs:
employees = Employee.find(params[:selected_subordinates])
employees.each do |e|
puts e.last_name
end