Lua.md

Lua Language

ScriptX and Lua language type comparison table

Lua	ScriptX
nil	Null
table	Object
table	Array
string	String
number	Number
boolean	Boolean
function	Function

1-based or 0-based?

The Lua language uses 1 as the base, but the C++ language uses 0 as the base. Therefore, in ScriptX, 0-based logic is still used for data operations.

such as:

Local<Array> arr;
arr.set(0, "hello");

// lua
arr[1] == "hello";

Lua functions with multiple return values

Lua functions support multiple return values, but the ScriptX API only supports returning Local<Value>.

When a Lua function returns multiple values, ScriptX will wrap the return value in an Array.

ByteBuffer

Lua language does not have ByteBuffer related API, so ScriptX provides a set of implementations through binding API.

At the same time, in the constructor of LuaEngine, users can also pass in their own delegate to implement ByteBuffer related APIs

instanceOf

Lua language does not have a built-in instanceof operator. In order to achieve the corresponding capabilities, ScriptX will add a ScriptX tool class globally in Lua.

ScriptX.isInstanceOf(instance, Class)

// C++
class InstanceOfTest: public script::ScriptClass {
 public:
  using ScriptClass::ScriptClass;
};

auto instanceOfTestDefine =
    defineClass<InstanceOfTest>("InstanceOfTest")
    .constructor()
    .build();

# lua
local ins = InstanceOfTest();
ScriptX.isInstanceOf(ins, InstanceOfTest) == true;

Binding MetaData of the class

Since Lua does not have a standard OO, for a ClassDefine, ScriptX will define the following declaration in Lua:

Class = {}

local staticMeta = {
    // constructor call
    __call = function()
      local ins = {};
      setmetatable(inx, instanceMeta);
      return ins
    end
}

for staticFunc do
 Class[staticFunc.name] = function() ... end
end

setmetatable(Class, staticMeta)

local instanceMeta = {
    __index = function()
      1. find from `ClassDefine.instanceProperty`
      2. find from `ClassDefine.instanceFunction`
      3. return nil
end

    __newindex = function()
      1. find from `ClassDefine.instanceProperty`
      2. raw set to table

    __gc = function()
      1. delete this
    end

instanceFunction = {...}

}

ScriptX.getInstanceMeta(Class) == instanceMeta;

For example, to extend a bound class, it can be as follows:

local meta = ScriptX.getInstanceMeta(Class)
function meta:__add() print(self, "add") end
function meta.instanceFunction:hello()
    print(self, "hello")
end

// test
local ext = Class()
x = ext + ext
ext:hello();

// output
table: 0x7fc873c18ed0 add
table: 0x7fc873c18ed0 hello