clojure rename-keys in nested structure - clojure

Question

Suppose I have a nested structure, something like this:
{:data1
{:categories [
{:name "abc" :id 234 :desc "whatever"}
{:name "def" :id 456 :desc "nothing"}]
}
:data2 {...}
:data3 {...}
}
And I need to transform the key names in the maps. I can transform the top level keys like this:
(rename-keys mymap {:data1 :d1})
But I'm not sure how to rename keys nested more deeply in the data structure (say I want to rename the :desc field to :description).
I'm pretty sure that zippers are the answer but can't quite figure out how to do it, or if there's a more straightforward way.

Answer 1

Same as Brian Carper's solution, except the walk namespace already has a specific function for this purpose. All keys at all levels are changed, be they nested inside any sort of collection or seq.
(:use 'clojure.walk)
(def x
{:data1
{:categories
[{:desc "whatever", :name "abc", :id 234}
{:desc "nothing", :name "def", :id 456}]},
:data2
{:categories
[{:desc "whatever", :name "abc", :id 234}
{:desc "nothing", :name "def", :id 456}]}})
(postwalk-replace {:desc :something} x)
{:data1
{:categories
[{:something "whatever", :name "abc", :id 234}
{:something "nothing", :name "def", :id 456}]},
:data2
{:categories
[{:something "whatever", :name "abc", :id 234}
{:something "nothing", :name "def", :id 456}]}}

Answer 2

postwalk is a pretty heavy sledgehammer in general, although it looks from your original question like you might need it. In many cases, you can perform updates in a nested structure with update-in:
user> (let [m {:foo {:deep {:bar 1 :baz 2}}}]
(update-in m [:foo :deep] clojure.set/rename-keys {:baz :periwinkle}))
{:foo {:deep {:periwinkle 2, :bar 1}}}

Answer 3

If you want to rename all :desc keys regardless of at which level of nesting they're located, this might work. If you only want to rename :desc keys at a certain level of nesting, you'll need something slightly more sophisticated.
This only works because clojure.set/rename-keys currently does nothing (returns its first argument untouched) if its first argument isn't a map.
user> (require '[clojure [set :as set] [walk :as walk]])
nil
user> (def x {:data1
{:categories
[{:desc "whatever", :name "abc", :id 234}
{:desc "nothing", :name "def", :id 456}]},
:data2
{:categories
[{:desc "whatever", :name "abc", :id 234}
{:desc "nothing", :name "def", :id 456}]}})
#'user/x
user> (walk/postwalk #(set/rename-keys % {:desc :description :id :ID}) x)
{:data1
{:categories
[{:name "abc", :ID 234, :description "whatever"}
{:name "def", :ID 456, :description "nothing"}]},
:data2
{:categories
[{:name "abc", :ID 234, :description "whatever"}
{:name "def", :ID 456, :description "nothing"}]}}
nil