OK - I have it now:
(map (fn [item product] (= (:product item (:id product))) [(:id item)
(:description product)]) items products)
This feels OK to me but if anyone has a nicer / more idiomatic solution, I
will be happy to take feedback.
ray
On Saturday, December 15, 2012 7:08:21 PM UTC+1, mond wrote:
>
> I think I am close to answering this myself (which is always nice!)
>
> I have done the necessary joins with map and I can return a product
> description
>
> user=> (map (fn [item product] (= (:product item (:id product)))
> (:description product)) items products)
> ("Men's Leather Slip on Brogues" "CK Y Fronts" "Slim Fit White Vest Shirt")
>
> Or a purchased status for the matching item
>
> user=> (map (fn [item product] (= (:product item (:id product)))
> (:purchased item)) items products)
> (true false true)
>
> But I have my knickers in a twist when I want to get more than one value
> out or a combination of values.
>
> user=> (map (fn [item product] (= (:product item (:id product))) (:id item
> :description product)) items products)
> (user=> IllegalArgumentException Wrong number of args passed to keyword:
> :id clojure.lang.Keyword.throwArity (Keyword.java:85)
>
> So does anyone have the last bit of syntax to help me take back a list of
> values from the inputs?
>
> Thanks
>
> ray
>
>
> On Saturday, December 15, 2012 5:25:59 PM UTC+1, mond wrote:
>>
>> I have defined these types of records for modelling a simple shopping
>> cart:
>>
>> ; An item in the cart
>> (defrecord Item [id name product quantity purchased])
>>
>> ; The product that relates to the item in the cart
>> (defrecord Product [id name description prices])
>>
>> ; A price definition
>> (defrecord Price [price tax-rate currency])
>>
>>
>> ; Sample items
>> (def items [
>> (->Item 1 "Brogues" "P-123" 1 true)
>> (->Item 2 "Underpants" "P-345" 1 false)
>> (->Item 3 "Shirt" "P-678" 1 true)
>> ])
>>
>> ; Sample products
>> (def products [
>> (->Product "P-123" "Brogues" "Men's Leather Slip on
>> Brogues" (->Price 93.00 21 "EURO"))
>> (->Product "P-345" "Underpants" "CK Y Fronts" (->Price
>> 23.50 21 "EURO"))
>> (->Product "P-678" "Shirt" "Slim Fit White Vest Shirt"
>> (->Price 45.99 21 "EURO"))
>> (->Product "P-1231" "Table" "Coffee Table" (->Price 375
>> 21 "EURO"))
>> (->Product "P-3451" "Chairs" "Set of Four(4) chairs"
>> (->Price 200 21 "EURO"))
>> (->Product "P-6781" "TableCloth" "Classic red and white
>> checks 2m x 2m" (->Price 17.99 21 "EURO"))
>> ])
>>
>> My requirement is to combine data from the two collections such that I
>> can show the detailed product information for any item, for example:
>>
>> (->Item 3 "Shirt" "Slim Fit White Vest Shirt" (->Price 45.99
>> 21 "EURO") 1 true)
>>
>> When I tried to use merge-with union I had an error which surprised me
>> since I thought records are also maps:
>>
>> user=> (merge-with union items products)
>> ClassCastException user.Product cannot be cast to java.util.Map$Entry
>> clojure.core/key (core.clj:1465)
>>
>> Although I will fight on, any tips from any of you that have done this
>> before would be greatly helped.
>>
>> Thanks
>>
>> ray
>>
>
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