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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