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125 lines
2.5 KiB
Markdown
125 lines
2.5 KiB
Markdown
# Lua语言
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ScriptX和Lua语言类型对照表
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| Lua | ScriptX |
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| :--: | :--: |
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| nil | Null |
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| table | Object |
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| table | Array |
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| string | String |
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| number | Number |
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| boolean | Boolean |
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| function | Function |
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## 1-based or 0-based?
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Lua语言使用1作为基数，但是C++语言是用0作为基数。因此在ScriptX中，对于数据等的操作，仍然使用0-based逻辑。
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比如:
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```c++
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Local<Array> arr;
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arr.set(0, "hello");
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// lua
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arr[1] == "hello";
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```
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## Lua函数多返回值
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Lua函数支持多返回值，但是ScriptX的API只支持返回 `Local<Value>`。
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当Lua函数返回多个值的时候，ScriptX会把返回值用Array包起来。
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## ByteBuffer
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Lua语言没有ByteBuffer相关的API，因此ScriptX通过 binding API提供了一套实现。
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同时在LuaEngine的构造函数里，使用者也可以传入自己的delegate实现ByteBuffer相关API
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## instanceOf
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Lua语言没有内建的 `instanceof` 操作符，为了实现相应能力，ScriptX会在Lua全局增加一个`ScriptX`工具类。
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`ScriptX.isInstanceOf(instance, Class)`
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```c++
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// C++
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class InstanceOfTest : public script::ScriptClass {
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public:
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using ScriptClass::ScriptClass;
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};
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auto instanceOfTestDefine =
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defineClass<InstanceOfTest>("InstanceOfTest")
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.constructor()
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.build();
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```
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``` lua
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# lua
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local ins = InstanceOfTest();
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ScriptX.isInstanceOf(ins, InstanceOfTest) == true;
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```
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## 绑定类的MetaData
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由于Lua没有标准的OO，对于一个ClassDefine，ScriptX会在lua中定义如下声明：
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```lua
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Class = {}
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local staticMeta = {
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// constructor call
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__call = function()
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local ins = {};
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setmetatable(inx, instanceMeta);
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return ins
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end
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}
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for staticFunc do
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Class[staticFunc.name] = function() ... end
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end
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setmetatable(Class, staticMeta)
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local instanceMeta = {
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__index = function()
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1. find from `ClassDefine.instanceProperty`
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2. find from `ClassDefine.instanceFunction`
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3. return nil
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end
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__newindex = function()
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1. find from `ClassDefine.instanceProperty`
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2. raw set to table
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__gc = function()
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1. delete this
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end
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instanceFunction = {...}
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}
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ScriptX.getInstanceMeta(Class) == instanceMeta;
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```
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比如，要扩展一个绑定的类，可以如下：
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```lua
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local meta = ScriptX.getInstanceMeta(Class)
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function meta:__add() print(self, "add") end
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function meta.instanceFunction:hello()
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print(self, "hello")
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end
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// test
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local ext = Class()
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x = ext + ext
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ext:hello();
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// output
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table: 0x7fc873c18ed0 add
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table: 0x7fc873c18ed0 hello
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```
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