A solution to arity problem when implementing an interface:
Interface:
(ns Agent.IAgent)
(gen-interface
:name "Agent.IAgent"
:methods [[senseEnv [int] int]]
)
Implementation:
(ns Agent.AgentIMP
(:gen-class :name "Agent.AgentIMP" :implements [Agent.IAgent]))
(defn -senseEnv [n]
10
)
Java program for testing:
import Agent.*;
public class testAgentIMP{
public static void main(String[] args){
AgentIMP AIMP = new AgentIMP();
System.out.println("senseEnv = " +
AIMP.senseEnv(5));
}
}
Result:
javac testAgentIMP.java
java testAgentIMP
>>> Exception in thread "main" java.lang.IllegalArgumentException: Wrong number
>>> of args passed to: AgentIMP$-senseEnv
Explanation: The method "-senseEnv" expects another first argument,
you can use "this":
(ns Agent.AgentIMP
(:gen-class :name "Agent.AgentIMP" :implements [Agent.IAgent]))
(defn -senseEnv [this n]
10
)
javac testAgentIMP.java
java testAgentIMP
>>> senseEnv = 10
The extra argument may not seem obvious from the interface
specification, therefore I post this solution.
But when using the above with clojure 1.2.0 and clojure-contrib 1.2.0,
I get the following error:
Exception in thread "main" java.lang.VerifyError: class Agent.AgentIMP
$loading__4410__auto__ overrides final method meta.()Lclojure/lang/
IPersistentMap;
I have inspected that class and the corresponding interface-class:
user=> (list-declared-methods "Agent.IAgent$loading__4410__auto__")
("public java.lang.Object Agent.IAgent$loading__4410__auto__.invoke()
throws java.lang.Exception" "public clojure.lang.IObj Agent.IAgent
$loading__4410__auto__.withMeta(clojure.lang.IPersistentMap)" "public
clojure.lang.IPersistentMap Agent.IAgent
$loading__4410__auto__.meta()")
user=> (list-declared-methods "Agent.AgentIMP$loading__4410__auto__")
("public java.lang.Object Agent.AgentIMP
$loading__4410__auto__.invoke() throws java.lang.Exception" "public
clojure.lang.IObj Agent.AgentIMP
$loading__4410__auto__.withMeta(clojure.lang.IPersistentMap)" "public
clojure.lang.IPersistentMap Agent.AgentIMP
$loading__4410__auto__.meta()")
I inspected the corresponding classes created with clojure/-contrib
1.1.0, and meta() was not a declared method there, only invoke() was
declared.
So, in clojure/-contrib 1.2.0, why does the class override method
meta() which is final in clojure.lang.Obj (though I was not able to
trace inheritance back to clojure.lang.Obj)?
Regards,
Tommy
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