Clojure 使用重载方法具体化 Java 接口(interface)

Question

我正在尝试在 Clojure 中实现以下 Java 接口(interface):

package quickfix;

public interface MessageFactory {
    Message create(String beginString, String msgType);
    Group create(String beginString, String msgType, int correspondingFieldID);
}

以下 Clojure 代码是我尝试执行此操作的尝试:

(defn -create-message-factory 
  []
  (reify quickfix.MessageFactory
    (create [beginString msgType]
      nil)
    (create [beginString msgType correspondingFieldID]
      nil)))

编译失败并出现错误:

java.lang.IllegalArgumentException: Can't define method not in interfaces: create

documentation建议重载接口(interface)方法是可以的，只要数量与本例中不同即可:

If a method is overloaded in a protocol/interface, multiple independent method definitions must be supplied. If overloaded with same arity in an interface you must specify complete hints to disambiguate - a missing hint implies Object.

我怎样才能让它工作？

Answer 1

您缺少一个参数。 reify 实现的每个方法的第一个参数是对象本身(defrecord/deftype 就是这种情况)。所以，试试这个:

(defn -create-message-factory 
  []
  (reify quickfix.MessageFactory
    (create [this beginString msgType]
      nil)
    (create [this beginString msgType correspondingFieldID]
      nil)))