Why not use the name of the class as the key? - James
On 18 May 2016 at 20:02, JvJ <[email protected]> wrote: > I'm creating an entity-component-system architecture. To use it, you > define component types, and put a bunch of components in a map to make an > entity. > > The rule for entities is that they can only have one component of any > given type, so I figured I would use the class to index it. However, since > this doesn't seem possible, > I think I'll just make my own "defcomponent" macro which acts almost like > defrecord, but makes sure that the constructor associates an appropriate > keyword type tag > in the metadata. > > Looking up the metadata is slightly slower than normal type reflection, > but I doubt it will make much of a difference. > > On Wednesday, 18 May 2016 11:43:22 UTC-7, Jason Felice wrote: >> >> I don't think there's a general workaround, and I'm not sure I have >> enough context to know what you are doing specifically. >> >> On Wed, May 18, 2016 at 2:28 PM, JvJ <[email protected]> wrote: >> >>> I suspected as much. It would be possible to mitigate the problem by >>> not using the repl, but I want the library I'm making to be built around a >>> repl-oriented workflow (like every good clojure library should). >>> >>> Is there any way around this, or do I have to resort to :type metadata? >>> >>> On Wednesday, 18 May 2016 11:07:37 UTC-7, Jason Felice wrote: >>>> >>>> When you reload a namespace with a record, the class for that record >>>> gets recreated. It will be functionally equivalent, but a different >>>> object. I'll bet that classes hash on identity. (Though if they hashed on >>>> name, you'd still have this problem.) >>>> >>>> On Wed, May 18, 2016 at 1:31 PM, JvJ <[email protected]> wrote: >>>> >>>>> I'm encountering a very strange error in some tests. >>>>> >>>>> The details are a bit complex, but I'm using type-indexed maps. >>>>> >>>>> So, given an object o, the map would be {(type o) o}. When I try to >>>>> lookup with the key (type o), I don't get the value, even though I can >>>>> clearly see it in the map. >>>>> >>>>> >>>>> I have a map instance called new-still in my tests, and I can clearly >>>>> see that this is its value >>>>> >>>>> {specs.core_test.Position {:x 0, :y 0}} >>>>> >>>>> >>>>> However, when I try to compare the first key to the Position class >>>>> (which it should be), I get this: >>>>> >>>>> >>>>> Fail in run-systems-tst >>>>> expected: (= (first (keys new-still)) Position) >>>>> actual: (not (= specs.core_test.Position specs.core_test.Position)) >>>>> >>>>> >>>>> >>>>> How is it that the class specs.core_test.Position is not equal to >>>>> itself?? >>>>> Is this a bug, or just some quirk of compilation? >>>>> >>>>> Thanks. >>>>> >>>>> -- >>>>> You received this message because you are subscribed to the Google >>>>> Groups "Clojure" group. >>>>> To post to this group, send email to [email protected] >>>>> Note that posts from new members are moderated - please be patient >>>>> with your first post. >>>>> To unsubscribe from this group, send email to >>>>> [email protected] >>>>> For more options, visit this group at >>>>> http://groups.google.com/group/clojure?hl=en >>>>> --- >>>>> You received this message because you are subscribed to the Google >>>>> Groups "Clojure" group. >>>>> To unsubscribe from this group and stop receiving emails from it, send >>>>> an email to [email protected]. >>>>> For more options, visit https://groups.google.com/d/optout. >>>>> >>>> >>>> -- >>> You received this message because you are subscribed to the Google >>> Groups "Clojure" group. >>> To post to this group, send email to [email protected] >>> Note that posts from new members are moderated - please be patient with >>> your first post. >>> To unsubscribe from this group, send email to >>> [email protected] >>> For more options, visit this group at >>> http://groups.google.com/group/clojure?hl=en >>> --- >>> You received this message because you are subscribed to the Google >>> Groups "Clojure" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to [email protected]. >>> For more options, visit https://groups.google.com/d/optout. >>> >> >> -- > You received this message because you are subscribed to the Google > Groups "Clojure" group. > To post to this group, send email to [email protected] > Note that posts from new members are moderated - please be patient with > your first post. > To unsubscribe from this group, send email to > [email protected] > For more options, visit this group at > http://groups.google.com/group/clojure?hl=en > --- > You received this message because you are subscribed to the Google Groups > "Clojure" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to [email protected] Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
