Hi,
thanks a lot! I ended putting the question in StackOverflow, yesterday, and
also got this answer. It would have took a while until I came up with this.
But now I understand.
For my concrete case I needed to update the record with all fields passed
in a map. So I did:
(commute items
#(mapv (fn [i]
(if (= (:id i) id)
(merge i params)
i))
%)))
Am Mittwoch, 9. April 2014 03:24:21 UTC+2 schrieb Leif:
>
> Hi, Ivan.
>
> (defn set-item-name [data id newname]
> (mapv #(if (not= (:id %) id) ; <- NB mapv keeps it a vector
> % ; no-op
> (assoc % :name newname))
> data))
>
> (dosync (commute items set-item-name 1 "foo"))
>
> This really only makes sense if :id is *not* actually a primary key in
> your data,
>
> If, however, :id *is* a primary key, and most of the operations on the
> data are only updating one element, you will want to follow Gary's advice
> and change your data to
>
> {1 {:id 1 :name ...}
> 2 {:id 2 :name ...}
> ...}
>
> I would also like to validate your feeling that this shouldn't be a
> one-liner; you can generalize 'set-item-name', and then if you do want to
> change the data structure later, you only have to change the general
> function.
>
> --Leif
>
> On Tuesday, April 8, 2014 7:10:13 PM UTC-4, Ivan Schuetz wrote:
>>
>> As I said I already looked in the docs, and know these basic examples,
>> but I don't know how to do:
>>
>> *"How can I say in a vector of records e.g. "set name of element to "foo"
>> where id is equal 1"?"*
>>
>>
>> The remove by Id works, I posted it only to show something which might be
>> similar to the update I'm looking for.
>>
>> I also wrote filter:
>>
>> (nth (filtered (filter #(= (:id %) id) @dataprovider/products)) 0)
>>
>> This gives me the element I need to update, but I still don't know how I
>> update this element in the vector.
>>
>>
>>
>> Am Mittwoch, 9. April 2014 00:27:41 UTC+2 schrieb Gary Trakhman:
>>>
>>> Maybe this will help:
>>>
>>> > (update-in [[] 2 3 4] [0] (constantly 1))
>>> [1 2 3 4]
>>>
>>> > (update-in [[] 2 3 4] [2] (constantly 1))
>>> [ [ ] 2 1 4]
>>>
>>> > (update-in [[] 2 3 4] [1] (constantly 1))
>>> [ [ ] 1 3 4]
>>>
>>> > (update-in [[] 2 3 4] [0 :a] (constantly :b))
>>> java.lang.IllegalArgumentException: Key must be integer
>>>
>>> > (update-in [[] 2 3 4] [0 0 :a] (constantly :b))
>>> [ [{:a :b}] 2 3 4]
>>>
>>>
>>> On Tue, Apr 8, 2014 at 6:22 PM, Ivan Schuetz <ivans...@gmail.com> wrote:
>>>
>>>> I would use merge to update the record with the map... but I don't know
>>>> how to get it from filter operation. Maybe I should not solve this with
>>>> 1-liner.
>>>>
>>>> Am Mittwoch, 9. April 2014 00:14:09 UTC+2 schrieb Ivan Schuetz:
>>>>
>>>>> Ahh dataprovider/products should be "items". Forgot to "simplify".
>>>>>
>>>>>
>>>>> Am Mittwoch, 9. April 2014 00:12:48 UTC+2 schrieb Ivan Schuetz:
>>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> sorry I don't get it. I just started learning Clojure.
>>>>>>
>>>>>> I did this to remove element with id 1
>>>>>>
>>>>>> (commute items #(remove (fn [x](= (:id x) id)) %))
>>>>>>
>>>>>> From your statement I understand update-in would work for the update,
>>>>>> but I don't know the syntax. Something like
>>>>>>
>>>>>> (commute dataprovider/products #(update-in % {:id id} (->Item
>>>>>> ???) ))
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> Am Mittwoch, 9. April 2014 00:01:00 UTC+2 schrieb Gary Trakhman:
>>>>>>>
>>>>>>>
>>>>>>>> But 1. Can't find examples with records, 2. Not sure if I can use
>>>>>>>> it to update a different field than the one I'm using to do the query.
>>>>>>>> In
>>>>>>>> the examples fields seem to be the same.
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>> Leave off the last path segment and return the full updated record,
>>>>>>> not just the new field's value.
>>>>>>>
>>>>>> --
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>>>
>>>
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