如何在 Clojure 中使用重载方法代理 Java 类？

发布于 2024-11-08 04:50:21 字数 668 浏览 0 评论 0原文

例如，给定一个如下 Java 类：

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

如何在 Clojure 中子类 Foo 并仅重写 bar(String) 方法，但重用原始 Foo 类中的 bar(Integer) 方法。像这样的东西（但这行不通）：

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

这个例子将打印：

with string:   my abc 
with integer:  my 10

但我想得到以下效果：

with string:   my abc 
with integer:  integer 10

原文

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

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倾听心声的旋律 2024-11-15 04:50:21

我猜这不是您的意思，但与此同时，您可以显式检查参数的类型并使用 proxy-super 调用 Foo 上的原始方法。

(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)))

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)))

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