They're not keyed by id because order in both the category and its items is
important. I could maintain the order explicitly, but that just makes other
problems like reordering more difficult.
As a couple people have suggested I could access the page using vector
indexing, but then I'd need to figure out what those induces are for the
category and the page given the item id. That seems reasonable, but I'm not
sure the best way to do that. I'm sure there's some python enumerate
equivalent where I can map all categories and items and filter down just
the pair with the matching item id.
On Jan 26, 2015 7:47 AM, "Michael Willis" <willismich...@gmail.com> wrote:
> Now that I think about it, I wonder why your categories aren't keyed by
> id, like this:
>
> (def categories [ {1 {:text "foo"} 2 {:text "bar" :ack 5}} {3 {:age 7}}])
>
> Then the update-in can take the category id, instead of having to know its
> index within a vector:
>
> (update-in categories [1 3] merge { :age 12 :somethingElse 29 })
> [{1 {:text "foo"}, 2 {:text "bar", :ack 5}} {3 {:age 12, :somethingElse
> 29}}]
>
>
> On Monday, January 26, 2015 at 9:42:56 AM UTC-6, Michael Willis wrote:
>>
>> (def categories [ [ { :id 1 :text "foo" } { :id 2 :text "bar" :ack 5 } ]
>> [ { :id 3 :age 7 } ] ])
>> #'user/categories
>> (update-in categories [1 0] merge { :age 12 :somethingElse 29 })
>> [[{:text "foo", :id 1} {:text "bar", :ack 5, :id 2}] [{:age 12,
>> :somethingElse 29, :id 3}]]
>>
>>
>> On Monday, January 26, 2015 at 8:54:58 AM UTC-6, Erik Price wrote:
>>>
>>> Many functions that affect keyed collections will work on vectors if you
>>> supply the numeric index as a key.
>>>
>>> e
>>>
>>> On Monday, January 26, 2015, Josh Stratton <stratto...@gmail.com> wrote:
>>>
>>>> I'm new to clojure and FP in general. One thing that has always been a
>>>> little confusing for me is working with immutable trees. I have a vector
>>>> of categories, each category containing a vector of items--each one a
>>>> hashmap. In that hashmap I have a bunch of attributes including an
>>>> item-id. Now, assuming I have an item id, what's the easiest way to update
>>>> the appropriate hashmap? I can't use an assoc, I believe, because my data
>>>> is in a vector--not keyed by the id.
>>>>
>>>> What I have been doing is writing a function that maps the categories
>>>> to new categories and then write another function that is called on every
>>>> item and updates it iff the item id matches. This works, but it seems
>>>> really clunky and I'm assuming there's a simpler way to do it.
>>>>
>>>> ; categories is a vector of item vectors, where the item is a hash
>>>> (def categories [ [ { :id 1 :text "foo" } { :id 2 :text "bar" :ack 5 }
>>>> ] [ { :id 3 :age 7 } ] ])
>>>>
>>>> Is there a more elegant workflow for updating categories? Let's say I
>>>> want to update item of id 3 with { :age 12 :somethingElse 29 }, what's the
>>>> easiest way to do this?
>>>>
>>>> ; so the return would be
>>>> [ [ { :id 1 :text "foo" } { :id 2 :text "bar" :ack 5 } ] [ { :id 3 :age
>>>> 12 :somethingElse 29 } ] ]
>>>>
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