如何与Cheerp/js中的外部变量交互? [英] How do I interface with extern variables from Cheerp/js?

问题描述

Cheerp 是js/wasm Transpiler的C ++. Screeps 是一款编程视频游戏.

Cheerp is a C++ to js/wasm transpiler. Screeps is a programming videogame.

如何阅读 Game.time 我已编译的C ++代码中的变量?(在蠕动中)

How do I read in the Game.time variable from my transpiled C++ code? (in screeps)

#include <cheerp/client.h>
#include <iostream>
using namespace std;

namespace client {
    class Game : public Object {
    public:
        static volatile double time;
    };  

    extern volatile Game &Game;
}

void webMain() {
    cout << __TIME__ << ": The current time is: " << client::Game.time << endl;
}

我尝试了多种变体形式:

I have tried any number of variations on:

• extern ， volatile 和 static
• 引用和指针
• client 和 cheerp 命名空间
• 从 Node / Object
继承
• int32_t 与 double 与 float 作为类型

• extern, volatile and static
• references and pointers
• both client and cheerp namespaces
• Inheriting from Node/Object
• int32_t vs double vs float as a type

我似乎得到了其中一个:

I seem to get either:

• NaN
• 0
• 1
• 已编译代码中的致命类型处理错误

如何在我的C ++代码中正确地与Javascript对象和变量交互?至少可以说，cheerp文档非常稀少...

How do I correctly interface with Javascript Objects and variables from within my C++ code? The cheerp documentation is VERY sparse to say the least...

注意:cheerp从未真正生成正确的Javascript.关于 Game 对象的处理方式始终存在一些不一致之处，并且在许多情况下，它错误地尝试将 Game.d 索引为数组而不是 Game.时间.

Note: cheerp is never actually generating the proper Javascript. There's always some inconsistency as to how the Game object is handled and in a lot of scenarios it's incorrectly trying to index Game.d as an array instead of Game.time.

推荐答案

在 client 名称空间中声明的类应该没有成员字段.

Classes declared in the client namespace should have no member fields.

要访问外部JS对象的属性，您需要添加以 get _ 和 set _ 开头的方法，以分别读取和写入该属性:

To access external JS objects properties you need to add methods starting with get_ and set_, to respectively read and write to the property:

#include <cheerp/client.h>
#include <iostream>
using namespace std;

namespace client {
    class Game : public Object {
    public:
        double get_time();
    };  

    extern Game &Game;
}

void webMain() {
    cout << __TIME__ << ": The current time is: " << client::Game.get_time() << endl;
}

此外，您无需在此处使用volatile.

Also, you don't need to use volatile here.

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