Clojure reify

•reify

(reify & opts+specs)

reify是一个宏，结构如下：

(reify options* specs*)

目前没有说明options，不需要指定。每个specs由协议或接口名及后跟的0个或多个方法体组成：

protocol-or-interface-or-Object

(methodName [args+] body)*

如果是协议或接口，需要提供所有的方法实现。如果是对象，还可以覆盖对象中的方法。需要说明的是，方法的第一个参数必须指定相应的目标对象，在Java语言中，就是“this”。

例子：

user=> (str (let [f "foo"]

#_=> (reify Object

#_=> (toString [this] f))))

"foo"

user=> (seq (let [f "foo"]

#_=> (reify clojure.lang.Seqable

#_=> (seq [this] (seq f)))))

(\f \o \o)

再来一个例子：

user=> (def server (reify

#_=> Server

#_=> (server-init [this]

#_=> (str "server init"))

#_=> (server-start [this]

#_=> (str "server start"))))

#'user/server

user=> (.server-init server)

"server init"

user=> (.server-start server)

"server start"

再来一个例子：

user=> (def def-fp (reify

#_=> Server

#_=> (server-init [this]

#_=> (str "server init"))

#_=> (server-start [this]

#_=> (str "server start"))

#_=> Client

#_=> (client-init [this]

#_=> (str "client init"))

#_=> (client-start [this]

#_=> (str "client start"))))

#'user/def-fp

user=> (class def-fp)

user$reify__1440

user=> (.server-init def-fp)

"server init"

user=> (.server-start def-fp)

"server start"

user=> (.client-init def-fp)

"client init"

user=> (.client-start def-fp)

"client start"

一个实际的例子：

•

defprotocol

core.clj:

;;;;
(ns clojure.wf.core
  (import java.util.function.Function)
  (:gen-class))

;;; control flow
;;; @see com.wf.core.AbstractControlFlow
(defprotocol AbstractControlFlow

  ;;
  (getFunctionExpress [this]))

TestFunction.java

import java.util.function.Function;

public class TestFunction implements Function<String, String> {

    public TestFunction() {
        System.out.println("test function");
    }

    public String apply(String s) {
        System.out.println(s);
        return s;
    }
}

(ns clojure.wf.test
  (import java.util.function.Function)
  (import com.wf.core.TestFunction)
  (:require [clojure.test :refer :all]
            [clojure.wf.core]))

;;;
(deftype AControlFlow [^Function functionExpress]
  clojure.wf.core/AbstractControlFlow

  (getFunctionExpress
    [this]
    functionExpress))


(deftest getFunctionExpressTest
  (println "testing clojure.wf.core.AControlFlow/getFunctionExpress[_]")


  (comment "
    testing clojure.wf.core.AControlFlow/getFunctionExpress[_]
    ...
  ")
  ;
  (def tfn (TestFunction.))
  ;
  (def a (AControlFlow. tfn))

  ; call fn getFunctionExpress
  (def functionExpress (.getFunctionExpress a))

  ; call fn apply
  (def result (.apply functionExpress "what..."))

  (println result))

>lein test :only clojure.wf.test/getFunctionExpressTest

lein test clojure.wf.test
testing clojure.wf.core.AControlFlow/getFunctionExpress[_]
test function
what...
what...

Ran 1 tests containing 0 assertions.
0 failures, 0 errors.

defprotocol 在定义方法的时候不能指定参数和返回类型。这在编译成java后全部映射为Object。

definterface

corex.clj

;;;;
(ns clojure.wf.corex
  (import java.util.function.Function)
  (:gen-class))

(definterface AbstractControlFlow

  ;; function express
  (^java.util.function.Function getFunctionExpress []))

TestFunction.java

import java.util.function.Function;

public class TestFunction implements Function<String, String> {

    public TestFunction() {
        System.out.println("test function");
    }

    public String apply(String s) {
        System.out.println(s);
        return s;
    }
}

corextest.clj

(ns clojure.wf.corextest
  (import java.util.function.Function)
  (import com.wf.core.TestFunction)
  (:require [clojure.test :refer :all]
            [clojure.wf.corex]))

;;;
(deftype AControlFlow [functionExpress]
  clojure.wf.corex.AbstractControlFlow

  (^Function getFunctionExpress
    [this]
    (println "fn getFunctionExpress called...")
    functionExpress))

(deftest getFunctionExpressTest
  (println "testing getFunctionExpress")


  (comment "
    testing getFunctionExpress
    ...
  ")
  ;
  (def tfn (TestFunction.))
  ;
  (def a (AControlFlow. tfn))

  ; call fn getFunctionExpress
  (def functionExpress (.getFunctionExpress a))

  ; call fn apply
  (def result (.apply functionExpress "what..."))

  (println result))

>lein test :only clojure.wf.corextest/getFunctionExpressTest

lein test clojure.wf.corextest
testing getFunctionExpress
test function
fn getFunctionExpress called...
what...
what...

Ran 1 tests containing 0 assertions.
0 failures, 0 errors.

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