ruby - Rails 3: use contents of an array as variables in a where method -

i have 3 models: isbn, sale , channel.

aim: list in isbns show.html.erb view looks this:

isbn: myisbn

total sales myisbn: 100

myisbn sales channel 1: 50

myisbn sales channel 2: 25

myisbn sales channel 3: 25

here 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 isbns controller, in show method, work. thought i'd refactor later - advice on whether of stuff should go in model 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 gets sales channel id 1 , isbn id 3. it's not use, ids hard coded. got channel ids array:

@channellist = channel.all @channel = 0 @channelarray = @channellist.map {|z| @channel = z.id} 

which gives me lovely array of [1,2,3,4]

but can't figure out how pass 1, 2, 3 , 4 block can used isbn's sales have sales channel id. tried (still hardcoding isbn id - thought i'd tackle 1 problem @ time), returned empty array:

@channelarray.each |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 going sum contents of array.

any gratefully received. first post, 0 acceptance rate change soon!

update

just finish question off, here's i've ended up, great, , ready tinkering with: array, nicely grouped, giving me sales isbn channel. group_by tip off!

#in show action in 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 console, line breaks added clarity:

(sneakily set @isbn = 3 first of all, since in console can't pass params view, @isbn instance defined in controller nil in 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, hash generated had key value pairs wrong way round. array containing sales data key - should have been value. rubydocs saved day:

@salesbychannel = @salesbychannelwrong.invert 

the invert method switches key-value pairs. sweet.

what you're looking passing array arel#where(), this:

sale.where(:sales_channel_id => @channelarray) 

this should execute in query. if that's not working, can pass array activerecord#find, this:

sale.find(@channelarray) 

hope helps