n00b question. I'm trying to loop through every User record in my database. The pseudo code might look a little something like this:
def send_notifications
render :nothing => true
# Randomly select Message record from DB
#message = Message.offset(rand(Message.count)).first
random_message = #message.content
#user = User.all.entries.each do
#user = User.find(:id)
number_to_text = ""
#user.number = number_to_text #number is a User's phone number
puts #user.number
end
end
Can someone fill me in on the best approach for doing this? A little help with the syntax would be great too :)
Here is the correct syntax to iterate over all User :
User.all.each do |user|
#the code here is called once for each user
# user is accessible by 'user' variable
# WARNING: User.all performs poorly with large datasets
end
To improve performance and decrease load, use User.find_each (see doc) instead of User.all. Note that using find_each loses the ability to sort.
Also a possible one-liner for same purpose:
User.all.map { |u| u.number = ""; puts u.number }
Related
I'm starting to know ROR and I was doing a kind of blog with articles, etc...
I did this code :
def show
id = params[:id]
list = Article.all
is_valid = false
list.all.each do |article|
if article.id == id
#is_valid = true
break
end
end
As you can see, this code just wants to check if the article ID exists or not. So I'm testing equality between id and article.id (which's a model linked to the appropriated table in the database) BUT when I try to use or display #is_valid boolean I saw that article.id == id is FALSE every time, even if article.id = 2 and id = 2. I tried to think about everything that can make this occuring, but I admit I still misunderstand this.
Then I ask you if you know why this is occuring. Of course, an equality like 2 == 2 will change #is_valid to true.
Thank you for your help !
Maybe its because params[:id] it's a string and article.id it's an Integer
(byebug) params
{"controller"=>"admin/my_controller", "action"=>"edit", "id"=>"1"}
And yes it is... "id" is a string "1", so you may try this:
def show
id = params[:id].to_i
list = Article.all
is_valid = false
list.all.each do |article|
if article.id == id
#is_valid = true
break
end
end
end
And maybe could work.
This is the answer to your question,
But if you want to learn a little more about Activerecord you can do this
Article.exists?(params[:id])
and that will do what you are trying to do just with a query against db.
and if you want to get just a simple article
record = Article.find_by(id: params[:id]) #return nil when not exist
if record # if nil will threat like false on ruby
#my code when exist
else
#my code when not exist
end
will work (you also can use find but find will throw an exception ActiveRecord::RecordNotFound when not exists so you have to catch that exception.
Activerecord has many ways to check this you dont need to do it by hand.
def show
#article = Article.find(params[:id])
end
This will create a database query which returns a single row. .find raises a ActiveRecord::NotFound exception if the record is not found. Rails catches this error and shows a 404 page. Article.find_by(id: params[:id]) is the "safe" alternative that does not raise.
Your code is problematic since list = Article.all will load all the records out of the database which is slow and will exhaust the memory on the server if you have enough articles. Its the least effective way possible to solve the task.
If you want to just test for existence use .exists? or .any?. This creates a COUNT query instead of selecting the rows.
Article.where(title: 'Hello World').exists?
Could someone take a look at my code and let me know if there is a better way to do this, or even correct where I'm going wrong please? I am trying to create a new row for each venue and variant.
Example:
venue_ids => ["1","2"], variant_ids=>["10"]
So, I would want to add in a row which has a venue_id of 1, with variant_id of 10. And a venue_id of 2, with variant_id of 10
I got this working, and it's now passing in my two arrays. I think I am almost there I'm not sure the .each is the right way to do it, but I think that I'm on the right track haha. I have it submitting, however, where would I put my #back_bar.save? because this might cause issues as it won't redirect
Thanks in advance.
def create
#back_bar = BackBar.new
#venues = params[:venue_ids]
#productid = params[:product_id]
#variants = params[:variant_ids]
# For each venue we have in the array, grab the ID.
#venues.each do |v|
#back_bar.venue_id = v
# Then for each variant we associate the variant ID with that venue.
#variants.each do |pv|
#back_bar.product_variant_id = pv
# Add in our product_id
#back_bar.product_id = #productid
# Save the venue and variant to the DB.
if #back_bar.save
flash[:success] = "#{#back_bar.product.name} has been added to #{#back_bar.venue.name}'s back bar."
# Redirect to the back bar page
redirect_to back_bars_path
else
flash[:alert] = "A selected variant for #{#back_bar.product.name} is already in #{#back_bar.venue.name}'s back bar."
# Redirect to the product page
redirect_to discoveries_product_path(#back_bar.product_id)
end
end # Variants end
end # Venues end
end
private
def back_bar_params
params.require(:back_bar).permit(:venue_id,
:product_id,
:product_variant_id)
end
as i said in comments
this is untested code and just showing you how it's possible to do with ease.
class BackBar
def self.add_set(vanue_ids, variant_ids)
values = vanue_ids.map{|ven|
variant_ids.map{|var|
"(#{ven},#{var})"
}
}.flatten.join(",")
ActiveRecord::Base.connection.execute("INSERT INTO back_bars VALUES #{values}")
end
end
def create
# use in controller
BackBar.add_set(params[:venue_ids], params[:variant_ids])
# ...
end
I have the following method in a controller:
# GET /units/1
def show
#unit = Unit.find(params[:id]
#product_instances = Array.new
current_user.product_instances.each do |product_instance|
if product_instance.product.unit == #unit
#product_instances.push(product_instance)
end
end
... #rest of method
end
As can be seen, I have four tables/models: User, Product, ProductInstance, and Unit. A User has many ProductInstances. Each ProductInstance maps to a Product. A Unit has many Products.
I would like to fetch only the User's ProductInstances that are linked to a Product in the current Unit. The current code does it, but how can I re-write it better? I'd like to get rid of the for-each loop and if statement and replace it with chained ActiveRecord queries, if possible.
I tried something like below but it didn't work:
#product_instances = current_user.product_instances.where(:product.unit => #unit)
Seems you cannot do :product.unit.
I think you can try this
current_user.product_instances.joins(:product).where("products.unit_id = ?",#unit.id)
or with hashes
current_user.product_instances.joins(:product).where(:products => {:unit_id => #unit.id})
I am creating a REST API in rails. I'm using RSpec. I'd like to minimize the number of database calls, so I would like to add an automatic test that verifies the number of database calls being executed as part of a certain action.
Is there a simple way to add that to my test?
What I'm looking for is some way to monitor/record the calls that are being made to the database as a result of a single API call.
If this can't be done with RSpec but can be done with some other testing tool, that's also great.
The easiest thing in Rails 3 is probably to hook into the notifications api.
This subscriber
class SqlCounter< ActiveSupport::LogSubscriber
def self.count= value
Thread.current['query_count'] = value
end
def self.count
Thread.current['query_count'] || 0
end
def self.reset_count
result, self.count = self.count, 0
result
end
def sql(event)
self.class.count += 1
puts "logged #{event.payload[:sql]}"
end
end
SqlCounter.attach_to :active_record
will print every executed sql statement to the console and count them. You could then write specs such as
expect do
# do stuff
end.to change(SqlCounter, :count).by(2)
You'll probably want to filter out some statements, such as ones starting/committing transactions or the ones active record emits to determine the structures of tables.
You may be interested in using explain. But that won't be automatic. You will need to analyse each action manually. But maybe that is a good thing, since the important thing is not the number of db calls, but their nature. For example: Are they using indexes?
Check this:
http://weblog.rubyonrails.org/2011/12/6/what-s-new-in-edge-rails-explain/
Use the db-query-matchers gem.
expect { subject.make_one_query }.to make_database_queries(count: 1)
Fredrick's answer worked great for me, but in my case, I also wanted to know the number of calls for each ActiveRecord class individually. I made some modifications and ended up with this in case it's useful for others.
class SqlCounter< ActiveSupport::LogSubscriber
# Returns the number of database "Loads" for a given ActiveRecord class.
def self.count(clazz)
name = clazz.name + ' Load'
Thread.current['log'] ||= {}
Thread.current['log'][name] || 0
end
# Returns a list of ActiveRecord classes that were counted.
def self.counted_classes
log = Thread.current['log']
loads = log.keys.select {|key| key =~ /Load$/ }
loads.map { |key| Object.const_get(key.split.first) }
end
def self.reset_count
Thread.current['log'] = {}
end
def sql(event)
name = event.payload[:name]
Thread.current['log'] ||= {}
Thread.current['log'][name] ||= 0
Thread.current['log'][name] += 1
end
end
SqlCounter.attach_to :active_record
expect do
# do stuff
end.to change(SqlCounter, :count).by(2)
I have an algorithm that searches through all of my sites users, finding those which share a common property with the user using the algorithm (by going to a certain page). It can find multiple users, each can have multiple shared properties. The algorithm works fine, in terms of finding the matches, but I'm having trouble working out how to store the data so that later I'll be able to use each unit of information. I need to be able to access both the found users, and each of the respective shared properties, so I can't just build a string. This is an example of the output, being run from the perspective of user 1:
user 4
sharedproperty3
sharedproperty6
user 6
sharedproperty6
sharedproperty10
shareproperty11
What do I need to do to be able to store this data, and have access to any bit of it for further manipulation? I was thinking of a hash of a hash, but I can't really wrap my head around it. I'm pretty new to programming, and Ruby in particular. Thanks for reading!
EDIT - Here's the code. I'm fully expecting this to be the most incorrect way to do this, but it's my first try so be gentle :)
So if I'm understanding you guys correctly, instead of adding the interests to a string, I should be creating an array or a hash, adding each interest as I find it, then storing each of these in an array or hash? Thanks so much for the help.
def getMatchedUsers
matched_user_html = nil
combined_properties = nil
online_user_list = User.logged_in.all
shared_interest = false
online_user_list.each do |n| # for every online user
combined_properties = nil
if n.email != current_user.email # that is not the current user
current_user.properties.each do |o| # go through all of the current users properties
n.properties.each do |p| # go through the online users properties
if p.interestname.eql?(o.interestname) # if the online users property matches the current user
shared_interest = true
if combined_properties == nil
combined_properties = o.interestname
else
combined_properties = combined_properties + ", " + o.interestname
end
end
end
if shared_interest == true
matched_user_html = n.actualname + ": " + combined_properties
end
end
end
end
return matched_user_html
render :nothing => true
end
This returns an array of hashes with all users and their corresponding sharedproperties.
class User
def find_matching_users
returning Array.new do |matching_users|
self.logged_in.each do |other_user|
next if current_user == other_user # jump if current_user
# see http://ruby-doc.org/core/classes/Array.html#M002212 for more details on the & opreator
unless (common_properties = current_user.properties & other_user.properties).empty?
matching_users << { :user => other_user, :common_properties => common_properties }
end
end
end
end
end
In your view you can do something like this:
<%- current_user.find_matching_users.each do |matching_user| -%>
<%-# you can acccess the user with matching_user[:user] -%>
<%-# you can acccess the common properties with matching_user[:common_properties] -%>
<%- end -%>
You can use a hash table with the key being the user object and the value being an array of the shared properties . This is assuming that you first need to do a lookup based on the user .
Something like this :
#user_results = { user1 => [sharedproperty3,sharedproperty7] , user2 => [sharedproperty10,sharedproperty11,sharedproperty12]}
You can then acces the values like :
#user_results[user1]
or you can also iterate over all the keys using #user_results.keys