Hi Daniel,
Thanks for your reply.
On 09/03/2011, at 11:57 AM, Daniel Solano Gomez wrote:
> On Wed Mar 9 11:16 2011, Andreas Kostler wrote:
>> Hi all,
>>
>> I need a macro to basically outputs this:
>>
>> (macroexpand '(chain-field-queries record "location" "name" "country"))
>> (. (. (. record (field "location")) (field "name")) (field "country"))
>>
>> Which chains method calls on a java object. e.g.
>> record.field("location").field("name").field("country"). etc...
>> so far so good. I though I could modify the .. macro for this:
>>
>> (defmacro chain-field-queries
>> ([x form] `(. ~x (field ~form)))
>> ([x form & more] `(chain (. ~x (field ~form)) ~@more)))
>>
>> However, this results in
>> (macroexpand '(chain-field-queries record "location" "name" "country"))
>> (. (. (. record (user/field "location")) (user/field "name")) (user/field
>> "country"))
>
> You could quote the field as a symbol:
>
> (defmacro chain-field-queries
> ([x form] `(. ~x (~'field ~form)))
> ([x form & more] `(chain-field-queries (. ~x (~'field ~form)) ~@more)))
Yes, I don't know why I wasn't thinking of doing that...
> Is a macro really required? You can do this as a function:
I think it is required. I'm trying to compose a query of the form
(defn make-native-query [db str foo]
(. (proxy [ONativeSynchQuery]
[db str foo]
(filter [rec]
(.. rec (field "location") (eq "Madrid") go))) run
objs))
Unfortunately, I'm bound to this style of query composition by the java api I'm
working with. So ideally, I'd like to be able to do something like
(select (where [[location eq "Madrid"]
and [name eq "Dhali"]])
And this would expand to
(defn make-native-query [db str foo]
(. (proxy [ONativeSynchQuery]
[db str foo]
(filter [rec]
(.. rec (field "location") (eq "Madrid") and (field
"name") (eq "Dhali") go))) run objs))
So, technically, I want something along the lines
(defn make-native-query [db str foo]
(. (proxy [ONativeSynchQuery]
[db str foo]
(filter [rec]
(.. rec (create-query [[location eq "Madrid"]
and
[name eq
"Dhali"]]) go))) run objs))
However, this doesn't seem to be possible. dot-dot doesn't evaluate the
create-query macro.
I must be missing something. If anyone could point me in the right direction :)
Andreas
> (defn chain-field-queries
> [record & fields]
> (let [query (fn [r f] (. r (field f)))]
> (reduce query record fields)))
>
> Sincerely,
>
> Daniel Solano Gómez
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