I have an unknown number of categories.
I want to pick one post from each category, and when there are no more categories I want to start from the beginning until I've reached a fixed number posts.
This is what I have, how could I rerun this iteration until I have my desired amount of posts?
desired_amount = 40
categories.each_with_index do |category, index|
post = category.posts.order(position: :asc)[index]
# do something with the post
return if desired_amount == (index + 1)
end
Personally, I would much prefer something like this:
posts = categories.cycle.take(desired_amount).each_with_index.map do |cat,ind|
cat.posts.order(position: :asc)[ind / categories.count]
end
That would give you the first post in each category, followed by the second post in each category, etc, until you had the number of posts you wanted. The one caveat is that if any category didn't have enough posts, your final array would have some empty spots in it (i.e. nils).
Maybe try something like this?
all_posts = []
#include posts to prevent constant querying the db
categories_with_posts = categories.includes(:posts)
until all_posts.size == 40
categories_with_posts.each do |category|
#pick a random post from current category posts
post = category.posts.order(position: :asc).sample
# add the post to collection if post is not nil
all_posts << post if post
# do something with the post
break if all_posts.size == 40
end
end
You could define an array of post before starting to loop:
desired_amount = 40
posts_array = []
unless posts_array.count == desired_amount
categories.each_with_index do |category, index|
post = category.posts.order(position: :asc)[index]
posts_array << post
return if desired_amount == (index + 1)
end
end
Related
I have an array PARTITION which stores days.
I want to group_by my posts (ActiveRecord::Relation) according to how old are they and in which partition they lie.
Example: PARTITION = [0, 40, 60, 90]
I want to group posts which are 0 to 40 days old, 40 to 60 days old, 60 to 90 days old and older than 90 days.
Please note that I will get array data from an external source and I don't want to use a where clause because I am using includes and where fires db query making includes useless.
How can I do this?
Here's a simple approach:
posts.each_with_object(Hash.new { |h, k| h[k] = [] }) do |post, hash|
days_old = (Date.today - post.created_at.to_date).to_i
case days_old
when 0..39
hash[0] << post
when 40..59
hash[40] << post
when 60..89
hash[60] << post
when 90..Float::INFINITY # or 90.. in the newest Ruby versions
hash[90] << post
end
end
This iterates through the posts, along with a hash which has a default value of an empty array.
Then, we simply check how many days ago a post was created and add it to relevant key of the hash.
This hash is then returned when all posts have been processed.
You can use whatever you want for the keys (e.g. hash["< 40"]), though I've used your partitions for illustrative purposes.
The result will be something akin to the following:
{ 0: [post_1, post_3, etc],
40: [etc],
60: [etc],
90: [etc] }
Hope this helps - let me know if you've got any questions.
Edit: it's a little trickier if your PARTITIONS are coming from an external source, though the following would work:
# transform the PARTITIONS into an array of ranges
ranges = PARTITIONS.map.with_index do |p, i|
return 0..(p - 1) if i == 0 # first range is 0..partition minus 1
return i..Float::INFINITY if i + 1 == PARTITIONS.length # last range is partition to infinity
p..(PARTITIONS[i + 1] - 1)
end
# loop through the posts with a hash with arrays as the default value
posts.each_with_object(Hash.new { |h, k| h[k] = [] }) do |post, hash|
# loop through the new ranges
ranges.each do |range|
days_old = Date.today - post.created_at.to_date
hash[range] << post if range.include?(days_old) # add the post to the hash key for the range if it's present within the range
end
end
A final edit:
Bit silly using each_with_object when group_by will handle this perfectly. Example below:
posts.group_by |post|
days_old = (Date.today - post.created_at.to_date).to_i
case days_old
when 0..39
0
when 40..59
40
when 60..89
60
when 90..Float::INFINITY # or 90.. in the newest Ruby versions
90
end
end
Assumptions:
This partitioning is for display purposes.
The attribute you want to group by is days
You want to the result a hash
{ 0 => [<Post1>], 40 => [<Post12>], 60 => [<Post41>], 90 => [<Post101>] }
add these methods to your model
# post.rb
def self.age_partitioned
group_by(&:age_partition)
end
def age_partition
[90, 60, 40, 0].find(days) # replace days by the correct attribute name
end
# Now to use it
Post.where(filters).includes(:all_what_you_want).age_partitioned
As per the description given in the post, something done as below could help you group the data:
result_array_0_40 = [];result_array_40_60 = [];result_array_60_90 = [];result_array_90 = [];
result_json = {}
Now, we need to iterate over values and manually group them into dynamic key value pairs
PARTITION.each do |x|
result_array_0_40.push(x) if (0..40).include?(x)
result_array_40_60.push(x) if (40..60).include?(x)
result_array_60_90.push(x) if (60..90).include?(x)
result_array_90.push(x) if x > 90
result_json["0..40"] = result_array_0_40
result_json["40..60"] = result_array_40_60
result_json["60..90"] = result_array_60_90
result_json["90+"] = result_array_90
end
Hope it Helps!!
I'm using Rails, but the underlying question here applies more broadly. I have a report page on my web app that allows the user to specify what they're filtering on, and query the database based on those filters (MongoDB).
The data is based around hotels, the user must first select the regions of the hotels (state_one, state_two, state_three), then the statuses of the hotels (planning, under_construction, operational), then an optional criteria, price range (200, 300, 400). Users can select multiple of each of these options.
My way of doing this currently is to create an empty array, iterate through each region, and push the region into the array if the user selected that region. Then, I'm iterating through THAT array, and assessing the status of the hotels in those regions, if any hotel has the status the user has selected, then I'm adding that hotel to a new empty array. Then I do the same thing for price range.
This works, but the code is offensively messy, here's an example of the code:
def find_hotel
hotels = find_all_hotels
first_array = []
hotels.each do |hotel|
if params[:options][:region].include? 'state_one' and hotel.state == :one
first_array.push(hotel)
elsif params[:options][:region].include? 'state_two' and hotel.state == :two
first_array.push(hotel)
elsif params[:options][:region].include? 'state_three' and hotel.state == :three
first_array.push(hotel)
end
end
second_array = []
first_array.each do |hotel|
if params[:options][:region].include? 'planning' and hotel.status == :planning
first_array.push(hotel)
elsif params[:options][:region].include? 'under_construction' and hotel.status == :under_construction
first_array.push(hotel)
elsif params[:options][:region].include? 'operational' and hotel.status == :operational
first_array.push(hotel)
end
end
third_array = []
second_array.each do |hotel|
# More of the same here, this could go on forever
end
end
What are some better ways of achieving this?
How about this:
STATES = [:one, :two, :three]
STATUSES = [:planning, :under_construction, :operational]
PRICES = [200, 300, 400]
def find_hotel
region = params[:options][:region]
first_array = set_array(region, find_all_hotels, STATES, :state)
second_array = set_array(region, first_array, STATUSES, :status)
third_array = set_array(region, second_array, PRICES, :price_range)
end
def set_array(region, array, options, attribute)
array.each_with_object([]) do |element, result|
options.each do |option|
result << element if region.include?(option) && element[attribute] == option
end
end
end
UPDATE
Added attribute parameter to set_array in order to make the code work with your updated example.
Since second_array is empty, whatever you get by iterating over it (perhaps third_array) would also be empty.
def find_hotel
hotels = find_all_hotels
first_array = hotels
.select{|hotel| params[:options][:region].include?("state_#{hotel.state}")}
first_array += first_array
.select{|hotel| params[:options][:region].include?(hotel.status.to_s)}
second_array = third_array = []
...
end
I have a collection/array in rails, transformed to json it looks like this:
#collection = [{"order_number":"123","item":"Paper"},{"order_number":"567","item":"Ruler"},{"order_number":"344","item":"Pen"},{"order_number":"342","item":"Pencil"},{"order_number":"877","item":"Keyboard"}]
I would like to pick the item with the order_number "342" and put it at the last position of the collection, so the new collection looks like this:
#collection = [{"order_number":"123","item":"Paper"},{"order_number":"567","item":"Ruler"},{"order_number":"344","item":"Pen"},{"order_number":"877","item":"Keyboard"},{"order_number":"342","item":"Pencil"}]
In theory, it would look like this:
#collection.last = #collection[3]
but that is obviously not fancy ruby style nor would it re-sort the array as in my example.
Also I don't know the index of the item as it can change depending on what the user shops.
how about:
#collection << #collection.delete_at[#collection.index{|x| x[:order_number] == "342"}]
This basically searches the index of element with :order_number 342 first, uses that index to delete it, and then store the deleted element at the end again.
You can also use the partition method:
#collection = #collection.partition { |h| h['order_number'] != '342' }.flatten
Just split your collection on two (without 342 order and with 342 order), then just join them. It should looks like:
#collection = #collection.select {|e| e[:order_number] != '342' } + #collection.select {|e| e[:order_number] == '342' }
If you have an index of an item it boils down to
#collection << #collection.delete_at(3)
If you don't, you could try finding it using
#collection.find_index{ |el| el["order_number"] == "123" }
Alternative you can try this too:
> #collection.each_with_index{ |key,value| #collection.push(#collection.delete_at(value)) if key[:order_number] == "344" }
#=>[{:order_number=>"123", :item=>"Paper"}, {:order_number=>"567", :item=>"Ruler"}, {:order_number=>"342", :item=>"Pencil"}, {:order_number=>"877", :item=>"Keyboard"}, {:order_number=>"344", :item=>"Pen"}]
This is my controller:
#trainings = Training.includes(:courses).order(:id, 'courses.order_id ASC')
In my view, for each training I need to loop for 3 times and check if has a course with column order_id with these values:
#trainings.each do |training|
for course_order in (1..3) do
this_course = training.courses.find_by(order_id: course_order)
# this_course.image(:resized) #i can print the paperclip image
end
end
The code above executes so many queries, so I tried using select method:
#trainings.each do |training|
for course_order in (1..3) do
this_course = training.courses.select { |course| course.order_id = course_order }
# this_course.image(:resized) #I cannot print paperclip image, because the result is an Array, so doesn't know the method "image"
end
end
So I have just one query, but I cannot call the image method from my Model, because the result is an Array object.
I know I can use:
training.courses.each do |course|
# course.image(:resized)
end
and I will get just one query, but I must loop 3 times, so when I dont have the row I can print a placeholder image, like:
Example image http://www.onrails.com.br/order_id.jpg
Your
this_course = training.courses.find_by(order_id: course_order)
returns first record that matches conditions, but
this_course = training.courses.select { |course| course.order_id == course_order }
selects all courses that match condition. If you want to find only the first one, use .detect instead of .select:
this_course = training.courses.detect { |course| course.order_id == course_order }
Also you have a typo. = is for assignment, == is for comparing.
I have created a loop, to calculate a total rating of a record. To do this I am first looping through all the child records (ratings), extracting the rating from each row, adding it to the total and then outputting the total.
<% total = 0 %>
<% for ratings in #post.ratings %>
<% total = (total + ratings.rating) %>
<% end %>
<%= total %>
My question is, simply, Is this the rails way?
It achieves the desired result, although needs 5 lines to do so. I am worried I am bring old habits from other languages into my rails project, and I am hoping someone could clarify if there is an easier way.
The following, preferably in the controller, will do it succinctly:
#rating = #post.ratings.sum { &:rating }
If that seems cryptic, you might prefer
#rating = #post.ratings.inject(0) { |sum, p| sum + p.rating }
Note, however, that this will fail if any of the ratings are null, so you might want:
#rating = #post.ratings.inject(0) { |sum, p| sum + (p.rating || 0) }
You should generally keep logic out of your views. I would put that code in a helper or a controller, and the call a method to calculate the total
Put the following in your controller, then you just need to use #rating in your view:
total = 0
#rating = #post.ratings.each { |r| total += r.rating }
Or you could move it into the Post model and do something like:
def self.total_rating
total = 0
ratings.each { |r| total += r.rating }
total
end
and then simply call #post.total_rating