When defining a struct type and instance, I can print the value and get the "struct" implementation type:
(defstruct person :name :age)
(def p (struct person "peter" 30))
user=> p
{:name "peter", :age 30}
user=> (type p)
clojure.lang.PersistentStructMap
But is it possible to tell whether p is an instance of the struct type "person"?
See: this post in the Clojure Google Group. In general the group archives are a treasure chest...
Note: The functionality of structs is replaced by records. Then this is not a problem anymore, because records really define new type and you can check with instance? whether something is of record of a certain type.
A bit ugly, but it works:
(require '[clojure.contrib.java-utils :as cj])
(defn struct-instance? [struct-def sm]
(= (cj/wall-hack-field clojure.lang.PersistentStructMap "def" sm)
struct-def))
(struct-instance? person p)
; => true
(struct-instance? person (conj p [:foo 1] [:bar 2]))
; => true
(defstruct foo :k1 :k2)
(struct-instance? foo p)
; => false
Stuff from clojure.contrib.java-utils will be available in 1.2 in part in clojure.java, in part in clojure.contrib.java (I guess?), and also in clojure.contrib.java-utils for backward compatibility... Although the details might still change. At any rate, Meikel is right about defrecord replacing defstruct, so if you're working on 1.2, prefer that.
