在Clojure中，如何读取Java类实例的公共成员变量？ [英] In Clojure how can I read a public member variables of an instance of a Java class?

问题描述

在Clojure中，如何读取Java类实例的公共成员变量？我想要类似的东西：

In Clojure how can I read a public member variables of an instance of a Java class? I want something like:

 (. instance publicMemberName)

我也尝试过：

instance/publicMemberName 

但这仅适用于静态方法

推荐答案

在Java中，类 java.awt.Point 具有公共字段 x 和 y 。请在此处查看Javadocs http://download.oracle.com /javase/6/docs/api/java/awt/Point.html 。

In Java, the class java.awt.Point has public fields x and y. See the javadocs here http://download.oracle.com/javase/6/docs/api/java/awt/Point.html.

在Clojure中，点宏适用于字段和方法。这对我有用：

In Clojure the dot macro works for fields and methods. This worked for me:

user=> (let [p (new java.awt.Point 2 4)] (.x p))
2

编辑：以下操作也有效（注意点和p之间的空格）：

The following also works (note the space between the dot and the p):

user=> (let [p (new java.awt.Point 2 4)] (. p x))
2

编辑：鉴于 java.awt.Point 具有方法 getX 和除了公共字段 x 和 y 之外的 getY 。所以去。首先，使Java类如下：

I decided to make a complete example given that java.awt.Point has methods getX and getY in addition to public fields x and y. So here goes. First make a Java class like this:

public class C {
    public int x = 100;
}

编译它

$ javac C.java

现在移动 C.class 到clojure目录中。接下来启动REPL，导入该类，并观察其工作：

Now move C.class into your clojure directory. Next start the REPL, import the class, and watch it work:

$ java -cp clojure.jar clojure.main
Clojure 1.2.0
user=> (import C)
C
user=> (let [q (new C)] (. q x))
100

请注意其他方式也可以：

Note the other way works too:

user=> (let [q (new C)] (.x q))
100

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