I have three models: Isbn, Sale and Channel.
Aim: to get a list in the isbns show.html.erb view which looks something like this:
Isbn: myisbn
Total sales for myisbn: 100
Myisbn sales for channel 1: 50
Myisbn sales for channel 2: 25
Myisbn sales for channel 3: 25
Here are my models. Isbn.rb model
has_many :sales
has_many :channels, :through => :sales
Sale.rb model (has attributes sales_channel_id, isbn_id, quantity)
has_many :channels
belongs_to :isbn
Channel.rb model:
belongs_to :sale
I've been working in the isbns controller, in the show method, just to get something to work. I thought I'd refactor later - advice on whether any of this stuff should go in the model would be most welcome.
So far I've got this:
@channelisbn = Sale.where("sales_channel_id =?',1).where("isbn_id=?",3)
@channelsalesisbn = 0
@channelisbn.each {|y| @channelsalesisbn =+ y.quantity}
This successfully gets all the sales where Channel ID is 1 and ISBN id is 3. But it's not much use, as the IDs are hard coded. So I got the Channel IDs into an array:
@channellist = Channel.all
@channel = 0
@channelarray = @channellist.map {|z| @channel = z.id}
which gives me a lovely array of [1,2,3,4]
But I can't figure out how to pass the 1, then the 2, then the 3 and then the 4 into a block which can be used to look up an ISBN's sales which have that sales channel id. This is what I tried (still hardcoding the ISBN id - thought I'd tackle one problem at a time), which returned an empty array:
@channelarray.each do |channel|
@channelisbn = []
@channelisbn = Sale.where("sales_channel_id = ?", channel).where("isbn_id = ?",3)
@channelsalesisbn = 0
@result = []
@result << @channelisbn.each {|a| @channelsalesisbn =+ a.quantity}
end
I was then going to sum the contents of the array.
Any help would be gratefully received. This is my first post, so my zero acceptance rate will change soon!
UPDATE
Just to finish this question off, here's where I've ended up, which is great, and ready for tinkering with: an array, nicely grouped, giving me sales by isbn by channel. Thanks for the group_by tip off!
#in the show action in the isbns controller:
@isbn = Isbn.find(params[:id])
@channelarray = Channel.select(:id).all
@channelarray.group_by {|i| Sale.where("channel_id = ?",i).where("isbn_id =?", @isbn)}
From the console, line breaks added for clarity:
(sneakily set @isbn = 3 first of all, since in the console you can't pass params from a view, so the @isbn instance defined in the controller is nil in the console)
ruby-1.9.2-p180 :067 > @channelarray.group_by {|i| Sale.where("channel_id = ?",i).where("isbn_id =?", @isbn)}
=> {[#<Sale id: 1, isbn_id: 3, quantity: 10000, value: 12000, currency: "GBP", total_quantity: nil, created_at: "2011-05-06 12:30:35", updated_at: "2011-05-07 17:43:13", customer: "Waterstone's", retail_price: nil, discount: nil, invoice_date: "2011-05-24">, #<Sale id: 2, isbn_id: 3, quantity: 1000, value: 500, currency: "GBP", total_quantity: nil, created_at: "2011-05-07 09:37:53", updated_at: "2011-05-07 19:14:52", customer: "Borders", retail_price: nil, discount: nil, invoice_date: "2011-02-05">]=>[#<Channel id: 1>],
[#<Sale id: 3, isbn_id: 3, quantity: 500, value: 1500, currency: "", total_quantity: nil, created_at: "2011-05-07 09:38:11", updated_at: "2011-05-07 19:15:07", customer: "Borders", retail_price: nil, discount: nil, invoice_date: "2011-12-05">, #<Sale id: 4, isbn_id: 3, quantity: 45, value: 300, currency: "", total_quantity: nil, created_at: "2011-05-07 09:38:38", updated_at: "2011-05-07 19:15:36", customer: "Borders", retail_price: nil, discount: nil, invoice_date: "2011-06-05">]=>[#<Channel id: 2>],
[]=>[#<Channel id: 3>],
[]=>[#<Channel id: 4>]}
UPDATE 2
Ha, the hash I generated had the key value pairs the wrong way round. The array containing the sales data was the key - it should have been the value. Rubydocs saved the day:
@salesbychannel = @salesbychannelwrong.invert
The invert method switches the key-value pairs. Sweet.
What you're looking for is passing an array to a ARel#where(), like this:
Sale.where(:sales_channel_id => @channelarray)
This should execute an IN query. If that's not working, you can always pass the array to ActiveRecord#find, like this:
Sale.find(@channelarray)
Hope this helps