I have a rails model that has a 'percentage' attribute
I would like to make sure the sum of of all 'percentage' is not > 100 when adding new values.
In my model, I have
validate :sum_can_not_exceed_hundred
def sum_can_not_exceed_hundred
if Result.all.sum(:percentage) > 100
errors.add(:base, :sum_can_not_exceed_hundred)
end
end
But this does not work for adding the records that are not on the db and those are are already saved.
Update:
The following seems to work, using a hint from Coderhs
if Result.where.not(id: self.id).sum(:percentage_share) + self.percentage_share > 100
errors.add(:base, :sum_can_not_exceed_hundred)
end
Since your table is new it won't be available on Result.all. Try modifying the code like so
validate :sum_can_not_exceed_hundred
def sum_can_not_exceed_hundred
sum = if self.id
Result.all.sum(:percentage)
else
self.percentage + Result.all.sum(:percentage)
end
errors.add(:base, :sum_can_not_exceed_hundred) if sum > 100
end
end
Related
I am iterating through a list of records. I need to check that if a record is first do XYZ and if not do ABC. Unfortunately I cant do this:
user = User.first
or
user = User.find(:id)
user.first?
Solution posted below
1. Make method to grab next and previous records
def next
[Model].where("id > ?", id).first
end
def prev
[Model].where("id < ?", id).last
end
2. Make method to check if record is first
def first?(record)
[Model].first == record
end
3. check if record is first
records.each do |record|
if record.first?(record)
record.update_attributes(attr: record.attr + record.attr)
else
prev_rec = [Model].find(record.id).prev
record.update_attributes(attr: prev_rec.attr + record.attr )
end
end
returns true or false
One improvement i would make sure that [Model].first is persistent so that it doesn't make a call to the database each time the loop is run.
I'm creating a picture-rating app where users can click on pictures and rate them on a scale from 1 to 5. I'm trying to calculate the average rating of a picture. Before when users clicked on a rating value, that value became the picture's rating.
Rating: 5
If a user clicked on 1, the rating would change to 1
Rating: 1
When reality, the rating should have been 3.
(5 + 1) / 2
=> 3
Here's what I've accomplished so far in implementing this feature.
I added a migration to create two new columns for my Pictures Table
rails g migration AddRatingsToPictures ratings_count: integer, rating_total: integer
Both the new attributes, ratings_count and rating_total are integer types, meaning they are assigned a nil value at default.
p = Picture.first
p.attribute_names
=> ['id', 'title', 'category', 'stars', 'updated_at', 'created_at',
'ratings_count', 'rating_total']
p.ratings_count
=> nil
p.rating_total
=> nil
My only problem is the NilClass Error.
Here is my update method in my PicturesController.
def update
#picture = Picture.find(params[:id])
#picture.ratings_count = 0 if #picture.stars.nil?
#picture.rating_total = #picture.stars
#picture.rating_total += #picture.stars if #picture.stars_changed?
#picture.ratings_count += 1 if #picture.rating_total_changed?
if #picture.update_attributes(picture_params)
unless current_user.pictures.include?(#picture)
#picture = Picture.find(params[:id])
current_user.pictures << #picture
redirect_to #picture, :flash => { :success => "Thank you! This picture has been added to your Favorites List" }
else
redirect_to :action => 'index'
flash[:success] = 'Thank you! This picture has been updated'
end
else
render 'edit'
end
end
Here is my picture_param method in my PicturesController
def picture_params
params.require(:picture).permit(:title, :category, :genre, :stars)
end
Here is what the two new columns do
ratings_count: Calculates the number of times a picture has been rated
rating_total: Calculates the sum of the stars a picture has received
In the above code, I first set the ratings_count to 0 if the picture doesn't have a rating. This means that the picture hasn't been rated yet.
I then need to initially set the rating_total to the number of stars a picture has. If a user changed the star rating, I would add those stars to the rating_total. And if the total increased, that's my cue to increase the number of ratings.
Obviously, to calculate the average, I'd do something like this.
(#picture.rating_total / #picture.ratings_count).to_f
Now, I think I have the right idea but I know why this doesn't work. When columns are created with an integer value, by default they are set to nil. This leads to a NilClass Error when I load the web page.
undefined method `/' for nil:NilClass
Here is my code in the View
<li><strong>Rating:</strong> <%= pluralize((#picture.rating_total / #picture.ratings_count), 'Star') %></li>
Ok, the main reason it is not working is because
you fetch the picture
you check the stars from the database, and the NOT the passed form-parameters
you do update_attributes, which if I am not mistaken, used to set attributes and then save the complete object, but since rails 4 only updates the passed attributes (which is what you would expect)
One small remark: keeping the rating correct is a function I would place in the model, NOT in the controller.
Furthermore, how to handle the if nil, initialise to zero I wrote a short blogpost about. In short: overrule the getter.
So I would propose the following solution. In your model write
class Picture < ActiveRecord::Base
def ratings_count
self[:ratings_count] || 0
end
def ratings_total
self[:ratings_total] || 0
end
def add_rating(rating)
return if rating.nil? || rating == 0
self.ratings_count += 1
self.ratings_total += rating
self.stars = self.ratings_total.to_f / self.ratings_count
self.save
end
def rating
return 0 if self.ratings_count == 0
self.ratings_total.to_f / self.ratings_count
end
and then the code in your controller becomes much cleaner and readable:
def update
#picture = Picture.find(params[:id])
stars = picture_params.delete(:stars)
if #picture.update_attributes(picture_params)
#picture.add_rating stars
unless current_user.pictures.include?(#picture)
current_user.pictures << #picture
redirect_to #picture, :flash => { :success => "Thank you! This picture has been added to your Favorites List" }
else
redirect_to :action => 'index'
flash[:success] = 'Thank you! This picture has been updated'
end
else
render 'edit'
end
end
I first delete the :stars from the parameters, because I do not want to save those, I want to use those for the add_rating. I then try to update_attributes, which will fail if there are any failing validations, and if that is ok, I will add_rating which itself will handle nil or zero correctly. Well granted: I do not know how you handle a "non-rating" (nil? zero?). It is possible a rating of zero should be added, because it will add a rating, but most UI I know do not allow to select 0 as rating, so you might want to change the zero handling.
This will handle the case of uninitialized (nil) values in your attributes...
def update
#picture = Picture.find(params[:id])
if #picture.stars_changed?
#picture.ratings_count = (#picture.ratings_count || 0) + 1
#picture.rating_total = (#picture.rating_total || 0) + ( #picture.stars || 0)
end
You don't need an array of ratings or ratings persisted to database, assuming you only count votes where the rating changes, you can accumulate the count and the total and divide the two (which is, in fact, what you're doing so I'm preaching to the converted).
Although it seems to me that if I change a picture from 5 to 1 and it only changes to 3, I'm gonna keep clicking 1 :)
You could set the default value on the migration when you created it. But no worries, you can create a new migration to change it:
# Console
rails g migration change_default_for_ratings_count_and_rating_total
# Migration Code
class ChangeDefaultForRatingsCountAndRatingTotal < ActiveRecord::Migration
def change
change_column :pictures, :ratings_count, :integer, default: 0
change_column :pictures, :rating_total, :integer, default: 0
end
end
Keep in mind that some databases don't automatically assign newly updated default values to existing column entries, so maybe you will have to iterate over every picture already created with nil values and set to 0.
Ok, an alternative...
Do an after_initialize so the fields are never, never, ever nil. Even if you're creating a new Picture object, they'll be initialized as zero. Problem will go away.
class Picture << ActiveRecord::Base
after_initialize do |picture|
picture.ratings_count ||= 0
picture.rating_total ||= 0
end
...
end
I'm using optimistic locking on a Rails model. Inside of a loop, I update and save this model (or, rather, many instances of this model).
From inside the loop, I output the "before" and "after" values, and the field appears to be updated correctly. But afterward, when I find the models by ID, I see that the field is not updated. Can anyone spot my error?
class Usage::LeadDistributionWeight < ActiveRecord::Base
attr_accessible :agent_id, :tag_value_id, :weight, :premium_limit, :countdown, :lock_version, :tag_value
def increment_countdown!
self.countdown = self.countdown + self.weight
save
rescue ActiveRecord::StaleObjectError
attempts_to_crement_countdown ||= 0
attempts_to_crement_countdown += 1
self.increment_countdown! unless attempts_to_crement_countdown > 5
false
end
def self.increment_countdowns parent_id, lead_type_id
if lead_type_id.present?
joins(:agent)
.where("#{reflect_on_association(:agent).table_name}.parent_id = ?", parent_id)
.where(tag_value_id:lead_type_id)
.all(readonly:false).each { |weight|
prev = weight.countdown
if weight.increment_countdown!
puts "#{prev} differs from #{weight.countdown}"
else
puts "no difference!"
end
}
end
end
end
I have a User model with Profit field. Profit field is a DECIMAL (11,0) type. I have a masked input on the form which allows user to input something like $1,000. I want to format that value and remove everything except numbers from it so i will have 1000 saved. Here is what i have so far:
class User < ActiveRecord::Base
before_save :format_values
private
def format_values
self.profit.to_s.delete!('^0-9') unless self.profit.nil?
end
end
But it keeps saving 0 in database. Looks like it is converting it to decimal before my formatting function.
Try this:
def profit=(new_profit)
self[:profit] = new_profit.gsub(/[^0-9]/, '')
end
First of all, this:
def format_values
self.profit.to_s.delete!('^0-9') unless self.profit.nil?
end
is pretty much the same as this:
def format_values
return if(self.profit.nil?)
p = self.profit
s = p.to_s
s.delete!('^0-9')
end
So there's no reason to expect your format_values method to have any effect whatsoever on self.profit.
You could of course change format_values to assign the processed string to self.profit but that won't help because your cleansing logic is in the wrong place and it will be executed after '$1,000' has been turned into a zero.
When you assign a value to a property, ActiveRecord will apply some type conversions along the way. What happens when you try to convert '$1,000' to a number? You get zero of course. You can watch this happening if you play around in the console:
> a = M.find(id)
> puts a.some_number
11
> a.some_number = 'pancakes'
=> "pancakes"
> puts a.some_number
0
> a.some_number = '$1,000'
=> "1,000"
> puts a.some_number
0
> a.some_number = '1000'
=> "1000"
> puts a.some_number
1000
So, your data cleanup has to take place before the data goes into the model instance because as soon as AR gets its hands on the value, your '$1,000' will become 0 and all is lost. I'd put the logic in the controller, the controller's job is to mediate between the outside world and the models and data formatting and mangling certainly counts as mediation. So you could have something like this in your controller:
def some_controller
fix_numbers_in(:profit)
# assign from params as usual...
end
private
def fix_numbers_in(*which)
which.select { |p| params.has_key?(p) }.each do |p|
params[p] = params[p].gsub(/\D/, '') # Or whatever works for you
end
end
Then everything would be clean before ActiveRecord gets its grubby little hands on your data and makes a mess of things.
You could do similar things by overriding the profit= method in your model but that's really not the model's job.
class User < ActiveRecord::Base
before_save :format_values
private
def format_values
self.profit = profit.to_s.gsub(/\D/,'') if profit
end
end
def format_values
self.profit.to_d!
end
I recommend you to write custom setter for this particular instance variable #profit:
class User
attr_accessor :profit
def profit= value
#profit = value.gsub(/\D/,'')
end
end
u = User.new
u.profit = "$1,000"
p u.profit # => "1000"
I would suggest using the rails helper of number with precision. Below is some code.
Generic Example:
number_with_precision(111.2345, :precision => 1, :significant => true) # => 100
Rails code Example:
def profit=(new_profit)
number_with_precision(self[:profit], :precision => 1, :significant => true)
end
How can I validate a number within a range dynamically using existing data?
For example - I have certain discounts on bulk ordering of products. If a customer buys 10-50 units they get X off and if they order 51-200 units Y off.
How can I validate this so that users can't put in quantity discounts over the same range?
I don't quite understand your question but I'm sure a custom validation would be one way to solve whatever you are trying to achieve. Simply add a validate method in your model like so:
def validate
self.errors.add(:amount, "is out of range") unless self.amount_in_allowed_range
end
private
def amount_in_allowed_range
# logic to return true or false
end
If I understand your question correctly then you are trying to avoid the creation of a discount range that overlaps an already existing one. The following code should do this for you
class QtyDiscount < ActiveRecord::Base
def validate
self.errors.add(:amount, "overlaps an existing range")
unless self.amount_in_allowed_range
end
def amount_in_allowed_range
# Check for overlapping ranges where our record either
# - overlaps the start of another
# - or overlaps the end of another
conditions = "
id != :id AND (
( min_value BETWEEN :min_value AND :max_value) OR
( max_value BETWEEN :min_value AND :max_value))"
puts "Conditions #{conditions}"
overlaps = QtyDiscount.find(:all, :conditions =>
[ conditions, { :id => self.id.nil? ? 0 : self.id,
:min_value => self.min_value,
:max_value => self.max_value} ])
overlaps.size == 0
end
end
EDITED
Removed an extraneous condition and added some checking for self.id to ensure we are not getting a false negative from our own record