I have got a model
class MyModel < ActiveRecord::Base
belongs_to :parent, :class_name => 'MyModel'
has_many :children, :class_name => 'MyModel', :foreign_key => 'parent_id'
end
And I want to grab all objects that have no parent and get them with all the children. In another words I want all parents and their children and children of their children and so on. So it has to be eager loaded recursively.
If I do
#result = MyModel.includes(:children)
.where('parent IS ?', nil)
I get only parents with the one level of children. But I dont get children of children. Is it possible to get all of them recursively? And is it possible to albo add counting the number of children for each parent?
I'd recommend you use a nested set gem like awesome_nested_set. That will give you a lot of functionality to help with handling sets to similar objects, and includes the facility to store children count.
You could recursively preload a set amount of self-joins by passing in a nested hash
#result = MyModel.includes(
children: {
children: {
children: {
children: :children
}
}
}
).where('parent IS ?', nil)
Or better yet generate this hash dynamically
This is untested (basically pseudo code)
scope :recursivly_include_children, -> (max_depth) {
includes(generate_nested_children_hash(max_depth))
}
def self.generate_nested_children_hash(current_hash = {}, level = 0, remaining_levels)
if remaining_levels > 0
// add one level to the current_hash here
generate_nested_children_hash(current_hash, level+1, remaining_levels-1)
else
current_hash
end
end
Then in the controller to get a maximum of 10 levels of preloaded children:
#result = MyModel.recursivly_include_children(10).where('parent IS ?', nil)
Related
I have a model whose rows I always want to sort based on the values in another associated model and I was thinking that the way to implement this would be to use set_dataset in the model. This is causing query results to be returned as hashes rather than objects, though, so none of the methods from the class can be used when iterating over the dataset.
I basically have two classes
class SortFields < Sequel::Model(:sort_fields)
set_primary_key :objectid
end
class Items < Sequel::Model(:items)
set_primary_key :objectid
one_to_one :sort_fields, :class => SortFields, :key => :objectid
end
Some backstory: the data is imported from a legacy system into mysql. The values in sort_fields are calculated from multiple other associated tables (some one-to-many, some many-to-many) according to some complicated rules. The likely solution will be to just add the values in sort_fields to items (I want to keep the imported data separate from the calculated data, but I don't have to). First, though, I just want to understand how far you can go with a dataset and still get objects rather than hashes.
If I set the dataset to sort on a field in items like so
class Items < Sequel::Model(:items)
set_primary_key :objectid
one_to_one :sort_fields, :class => SortFields, :key => :objectid
set_dataset(order(:sortnumber))
end
then the expected clause is added to the generated SQL, e.g.:
>> Items.limit(1).sql
=> "SELECT * FROM `items` ORDER BY `sortnumber` LIMIT 1"
and queries still return objects:
>> Items.limit(1).first.class
=> Items
If I order it by the associated fields though...
class Items < Sequel::Model(:items)
set_primary_key :objectid
one_to_one :sort_fields, :class => SortFields, :key => :objectid
set_dataset(
eager_graph(:sort_fields).
order(:sort1, :sort2, :sort3)
)
end
...I get hashes
?> Items.limit(1).first.class
=> Hash
My first thought was that this happens because all fields from sort_fields are included in the results and maybe if selected only the fields from items I would get Items objects again:
class Items < Sequel::Model(:items)
set_primary_key :objectid
one_to_one :sort_fields, :class => SortFields, :key => :objectid
set_dataset(
eager_graph(:sort_fields).
select(:items.*).
order(:sort1, :sort2, :sort3)
)
end
The generated SQL is what I would expect:
>> Items.limit(1).sql
=> "SELECT `items`.* FROM `items` LEFT OUTER JOIN `sort_fields` ON (`sort_fields`.`objectid` = `items`.`objectid`) ORDER BY `sort1`, `sort2`, `sort3` LIMIT 1"
It returns the same rows as the set_dataset(order(:sortnumber)) version but it still doesn't work:
>> Items.limit(1).first.class
=> Hash
Before I add the sort fields to the items table so that they can all live happily in the same model, is there a way to tell Sequel to return on object when it wants to return a hash?
If you use #eager_graph, you must use #all instead of #each to retrieve the results in order for the graph to be processed (since you cannot eagerly load without having all instances up front), or use the eager_each plugin (which makes #each call #all internally).
I have the following scopes defined in my model:
scope :upcoming, -> { where(:start_time.gt => Time.now).asc(:start_time) }
scope :in_progress, -> {
now = Time.now
where(:start_time.lte => now).where(:end_time.gte => now).asc(:start_time)
}
I want to create another scope that combines the results of both of those scopes called current. I tried something like this:
scope :current, -> { self.in_progress | self.upcoming }
But this just ends up treating them both like arrays and concatenating them. The problem with this is that when I try to call my scope with Model.current, I get the following error message:
NoMethodError: undefined method `as_conditions' for #<Array:0xaceb008>
This is because it converted the Mongoid Criteria object to an array, but I don't want that. I want the object to stay as a Mongoid Criteria object.
What I really want is the union of the in_progress set and the upcoming set.
Any ideas? Thanks.
You can try to compose your criteria using Mongoid's query methods and dereferencing into the criteria's selector, but I wouldn't necessarily recommend this -- see below for an example. I second the recommendation to craft your third scope. Remember that these scopes correspond to db queries that you want to be efficient, so it is probably worth your time to examine and understand the resulting and underlying MongoDB queries that are generated.
Model
class Episode
include Mongoid::Document
field :name, type: String
field :start_time, type: Time
field :end_time, type: Time
scope :upcoming, -> { where(:start_time.gt => Time.now).asc(:start_time) }
scope :in_progress, -> {
now = Time.now
where(:start_time.lte => now).where(:end_time.gte => now).asc(:start_time)
}
scope :current, -> { any_of([upcoming.selector, in_progress.selector]) }
scope :current_simpler, -> { where(:end_time.gte => Time.now) }
end
Test
require 'test_helper'
class EpisodeTest < ActiveSupport::TestCase
def setup
Episode.delete_all
end
test "scope composition" do
#p Episode.in_progress
#p Episode.upcoming
#p Episode.current
#p Episode.current_simpler
in_progress_name = 'In Progress'
upcoming_name = 'Upcoming'
Episode.create(:name => in_progress_name, :start_time => Time.now, :end_time => 1.hour.from_now)
Episode.create(:name => upcoming_name, :start_time => 1.hour.from_now, :end_time => 2.hours.from_now)
assert_equal([in_progress_name], Episode.in_progress.to_a.map(&:name))
assert_equal([upcoming_name], Episode.upcoming.to_a.map(&:name))
assert_equal([in_progress_name, upcoming_name], Episode.current.to_a.map(&:name))
assert_equal([in_progress_name, upcoming_name], Episode.current_simpler.to_a.map(&:name))
end
end
You have to map your Array back to a Mongoid::Criteria.
Any array of yours can be translated to a criteria with any_in:
scope :has_data, -> { any_in(:_id => all.select{ |record| record.data.size > 0 }.map{ |r| r.id }) }
So, something like this should do the trick: (untested)
scope :current, -> { any_in(:_id => (self.in_progress + self.upcoming).map{ |r| r.id }) }
I hope there exists better solutions, but this solves the equation at least.
I am sorry if I am asking the question poorly. I have a Rails 3.1 app with models (simplified) like so:
class Employee < ActiveRecord::Base
has_many :merged_children, :class_name => 'Employee', :foreign_key => "merge_parent_id"
has_many :timesheets
def total_time
merged_children.timesheets.in_range(range).hours_minutes.sum
end
end
class Timesheet < ActiveRecord::Base
belongs_to :employee
def in_range(range)
# filter records based on transaction_date in range
end
def hours_minutes
(hours + minutes/60.0).to_f
end
end
Note: The in_range method acts as a scope, essentially, and hours_minutes is a calculation. hours_minutes is valid for each timesheet record in the resulting dataset, and then total_time should sum those values and return the amount.
The "total_time" method is not working because employee.merged_children returns an array and timesheets is meant to run against a single Employee object.
Is there any way to structure the "total_time" so that it still sends one query to the db? It seems inelegant to iterate over the merged_children array, issuing a query for each. Not sure if a direct call to an Arel table would help or hurt, but I am open to ideas.
If we get it right, the resulting SQL should effectively look something like:
SELECT sum(hours + minutes/60.0)
FROM employees e1 join employees e2 on e1.id = e2.merge_parent_id join timesheets t on t.employee_id = e2.id
WHERE e1.id = [#employee.id] and t.transaction_date BETWEEN [#range.begin] and [#range.end]
Thanks so much!
The easiest thing here might be to add
has_many :children_timesheets, :through => :merged_children, :source => :timesheets
To your employee model,
Then (assuming in_range is actually a scope, or a class method that does a find)
children_timesheets.in_range(...)
Should be the collection of timesheets you're interested in and you can do something like
children_timesheets.in_range(...).collect(&:hours_minutes).sum
Untested with actual data.
range = ((1.day.ago)...(2.days.ago))
merge_parent = Employee.find(some_id)
Timesheet.where(:transaction_date => range)
.joins(:employee).where(:employees => {:merge_parent_id => merge_parent.id})
.sum('hours*60 + minutes')
(0.3ms) SELECT SUM(hours*60 + minutes) AS sum_id FROM "timesheets" INNER JOIN "employees" ON "employees"."id" = "timesheets"."employee_id" WHERE "employees"."merge_parent_id" = 1 AND ("timesheets"."created_at" >= '2011-12-13 03:04:35.085416' AND "timesheets"."created_at" < '2011-12-12 03:04:
Returns "0" for me. So hopefully it will return something nicer for you
I hope I am asking this right, so please let me know if I'm way off.
The problem is trying to build a homepage that draws from multiple controllers, to display the nearest locations from multiple controllers, ie. food, businesses, ect.
Right now the individual listings pages have maps drawn from their respective
#json = Controller.all.to_gmaps4rails
How would I do something like :
#json = Controller1 Controller2 .all.to_gmaps4rails
I hope this isnt a noob question and I'm just having a bad day. Thanks guys!
edit 12.5.2011 #seanhill - this is one of the models, the other sections are very close to this format. First off, I wasn't even sure if my homepage requires it's own model, as it doesn't interact with the db at all, more pulling data from controllers that do the work. Thanks for the response Sean!
class Dining < ActiveRecord::Base
validates_uniqueness_of :name, :message => "already exists"
attr_accessible :name, :address, :cuisine, :latitude, :longitude, :about, :facebook, :twitter, :phone, :website
geocoded_by :address
after_validation :geocode, :if => :address_changed?
acts_as_gmappable :process_geocoding => false
def gmaps4rails_address
"#{self.address}"
end
def gmaps4rails_infowindow
"<h3>#{self.name}</h3><br /><h5>#{self.cuisine}</h5>"
end
def self.search(search)
if search
where('name LIKE ?', "%#{search}%")
else
scoped
end
end
end
Try this
holder = Controller1.all
holder << Controller2.all
#json = holder.flatten.map{|h| {lng: h.longitude, lat: h.latitude, class: h.class.to_s}}.to_json
Make sure to change longitude and latitude based on your column names and use js to manipulate the markers based upon class.
As the #Sean Hill said you shouldn't be calling .all on controllers but I think you have a slight misunderstanding of how things are working. Assuming you have a Model called Dining and another called Shop, when you call Dining.all or Shop.all inside class DiningsController < ApplicationController, you are calling .all on either the Dining Model or the Shop Model not on the DiningsController.
The information you display through a controller is only limited by the methods you call in it although it is best practice ensure the main focus of the information displayed is related to the respective controller.
So what you are really trying to do is get the records from multiple models and group them together to display them in a single map.
With that said the answer should read something like this
holder = Dining.all # Takes all Dining records returned as an array and sets them to holder variable
holder << Shop.all # Pushes the Shop records array into the holder with the dining records
holder.flatten!# Next we flatten the array so we only have a single array.
# Then we use the map method to run the given code one time for each instance
# in the holder array to extract the info we need. The results for every instance
# in holder are returned in an array which we then convert to_json.
#json = holder.map{|h| {lng: h.longitude, lat: h.latitude, class: h.class.to_s}}.to_json
#json1 = something.to_gmaps4rails
#json2 = something.to_gmaps4rails
#json = (JSON.parse(#json1) + JSON.parse(#json2)).to_json
I populated the map with my initial data of festivals, and then added the rides to it with javascript with this code,
<% content_for :scripts do %>
<script type="text/javascript">
Gmaps.map.callback = function() {
$.getJSON('/rides_gmap', function(data){
Gmaps.map.addMarkers(data);
});
}
</script>
<%end%>
In the rides controller I had this
def rides_gmap
#rides = Ride.all
#json = #rides.to_gmaps4rails do |ride, marker|
marker.infowindow render_to_string(:partial => "/rides/infowindow", :locals => { :ride => ride})
marker.picture({
'picture' => view_context.image_path("orange-dot.png"),
'width' => 20,
'height' => 20
})
marker.title "#{ride.address}"
marker.json({:ride_id => ride.id, :ride_festivaltype => ride.festival.festivaltype
end
respond_with #json
end
I hope this helps.
I iterate through all cars and its supported attributes (many attributes per car) to create a structure like this, how do I do this in a dynamic fashion.
cars = {
"honda" => {'color' => 'blue', 'type' => 'sedan'}.
"nissan" => {'color' => 'yellow', 'type' => 'sports'}.
...
}
cars.each do |car|
car_attrs = ...
car_attrs.each do |attr|
??? How to construct the above structure
end
end
Your question is not very clear... But i guess this is what you want:
cars = {}
options = {}
options['color'] = 'blue'
...
cars['honda'] = options
Is that what you were looking for?
It sounds like you may be asking for a way to create a 2-dimensional hash without having to explicitly create each child hash. One way to accomplish that is by specifying the default object created for a hash key.
# When we create the cars hash, we tell it to create a new Hash
# for undefined keys
cars = Hash.new { |hash, key| hash[key] = Hash.new }
# We can then assign values two-levels deep as follows
cars["honda"]["color"] = "blue"
cars["honda"]["type"] = "sedan"
cars["nissan"]["color"] = "yellow"
cars["nissan"]["type"] = "sports"
# But be careful not to check for nil using the [] operator
# because a default hash is now created when using it
puts "Found a Toyota" if cars["toyota"]
# The correct way to check would be
puts "Really found a Toyota" if cars.has_key? "toyota"
Many client libraries assume that the [] operator returns a nil default, so make sure other code doesn't depend on that behavior before using this solution. Good luck!
Assuming you are using something similar to ActiveRecord (but easy to modify if you are not):
cars_info = Hash[cars.map { |car| [car.name, car.attributes] }