java - 从Luaj继承Java类

Question

在 Luaj 中，是否可以让 Lua 类扩展 Java 类？我尝试在绑定(bind)类上使用 getmetatable() ，但显然它返回 nil 。

这里，Wizard是绑定(bind)到Lua的Java类，SetupWizard是我要继承Wizard的Lua类。

function SetupWizard:new()
    local self = setmetatable({}, getmetatable(Wizard))
    return self
end

将 __index 分配给 Wizard 的值也不起作用。

SetupWizard 定义:

SetupWizard = {
    host = nil,
    user = nil,
    password = nil,
    database = nil,
    mySqlTables = {
        users = nil,
    },
}
SetupWizard.__index = Wizard

... SetupWizard methods here

Answer 1

LuaJ 在如何处理诸如从 java 导入类之类的事情方面相当灵活。您尚未指定如何完成此操作，因此我假设您已通过创建 library of Java Functions 来完成此操作。作为构建您可以需要的模块的桥梁(使用 require"moduleName")，如下所示:

import org.luaj.vm2.LuaValue;
import org.luaj.vm2.lib.OneArgFunction;
import org.luaj.vm2.lib.TwoArgFunction;


/*
 * When require"module name" is called in luaJ it also searches for java classes with a classname that matches
 * the given module name that inherit from LuaFunction and have a default constructor, it then
 * calls the method call(LuaValue moduleName, LuaValue globalEnviroment) passing the module name string and
 * global environment as LuaValues and returning the return value of this call as it's own. 
 * 
 */

public class Example extends TwoArgFunction{

    @Override
    public LuaValue call(LuaValue modname, LuaValue globalEnv) {
        // Creates a table to place all our functions in
        LuaValue table = LuaValue.tableOf();

        // Sets the value 'name' in our table to example. This is used in the example function
        table.set("name", "example");
        // Sets the value 'exampleMethod' in our table to the class of type OneArgFunction
        // we created below
        table.set("exampleMethod", exampleMethod);

        //Finally returns our table. This value is then returned by require.
        return table;
    }


    /* Creates a function that takes one arg, self.

      This emulates the creation of a method in lua and can be called,
      when added to a table, as table:exampleMethod().
      This is possible as in Lua the colon in functions is
      Syntactic suger for object.function(object) 

    */
    OneArgFunction exampleMethod = new OneArgFunction() {

        @Override
        public LuaValue call(LuaValue self) {

            if(self.istable()) {
                return self.get("name");
            }

            return NIL;
        }
    };

}

然后可以在您的 Lua 代码中使用它，如下所示:

--Imports the class Wrapper we created
example = require"Example"
--Prints the return value of calling exampleMethod
print("The name of the class is: "..example:exampleMethod())


--And then used as an index like so
example2 = setmetatable({},{__index=example})

example2.name = "example2"

print("The name of the class is: "..example2:exampleMethod())

正如我在答案顶部所说，LuaJ 在如何处理这些事情方面是灵活的，这只是我会做的方式。

由于我的声誉，我无法发表评论询问您的导入情况如何LuaJ 中的 Java 类，请随时在对此答案的评论中进行澄清。