如何在Clojure中使用重载方法代理Java类？

Question

For example, given a Java class like:

public class Foo {
  public String bar(String x) {
    return "string " + x;
  }
  public String bar(Integer x) {
    return "integer " + x;
  }
}

How can I subclass Foo in Clojure and override only the bar(String) method but reuse the bar(Integer) from the original Foo class. Something like this (but this won't work):

(let [myFoo (proxy [Foo] [] 
              (bar [^String x] (str "my " x)))]
  (println "with string:  " (.bar myFoo "abc"))
  (println "with integer: " (.bar myFoo 10)))

This example will print:

with string:   my abc 
with integer:  my 10

but I would like to get the effect of:

with string:   my abc 
with integer:  integer 10

Answer 1

I'm guessing this is not what you meant, but in the meantime, you can explicitly check the type of the argument and use proxy-super to call the original method on Foo .

(let [myFoo (proxy [Foo] [] 
              (bar [x]
                (if (instance? String x)
                  (str "my " x)
                  (proxy-super bar x))))]
  (println "with string:  " (.bar myFoo "abc"))
  (println "with integer: " (.bar myFoo 10)))