luaplus 与官方文档慢慢扯(六)

 

Calling Functions(调用lua函数)

 

LuaObject 尝试简化Lua API 接口函数

它做到了完全屏蔽掉堆栈方面的操作 

一般情况下,调用Lua的函数可以在一行代码中完成

Recommended Style(推荐风格)

利用一些c++模板的技巧,使我们调用lua函数好像是在调用普通的c++函数

LuaStateOwner state; state->DoString("function Add(x, y) return x + y end"); LuaFunction<float> Add = state->GetGlobal("Add"); printf("Add: %d/n", Add(2, 7));  

模板 LuaFunction<RT> 带有一个参数 RT (return type)  ,意思是返回值类型

参数类型可以自动判断,但是返回值不行, 所以需要手动设置返回值类型 默认的返回值类型是 void

LuaStateOwner state; state->DoString("function Print(str) print(str) end"); LuaFunction<> Print = state->GetGlobal("Print"); Print("Hello, world!");  

LuaPlus可以使用的内置返回值类型有

• bool
• char
• unsigned char
• short
• unsigned short
• int
• unsigned int
• long
• unsigned long
• float
• double
• const char*
• const lua_WChar*
• lua_CFunction
• LuaStateCFunction
• LuaStackObject
• LuaObject
• const void*
• LuaArgNil()
• LuaLightUserData(pointer)
• LuaUserData(pointer)

 

与直接注册c++普通函数一样 调用lua函数同样只支持最多7个参数

 

 

Iostream-like Style(Iostream-like 风格)(iostream这部分基本不懂...)

LuaPlus also employs a convention similar to the Standard C++ library's iostream functionality.  A simple example follows:

LuaStateOwner state; state->DoString("function Add(x, y) return x + y end"); LuaObject funcObj = state->GetGlobal("Add"); { LuaAutoBlock autoBlock(state); LuaCall call = funcObj(); LuaStackObject retObj = call << 2 << 7 << LuaRun(); printf("Add: %d/n", retObj.GetInteger()); }  

 

The function call starts by "calling" the LuaObject.  LuaObject provides an overloaded function operator().  Then, each argument to the function is added to the argument list, left to right.  Finally, when all arguments are added, LuaRun() executes the function call.

It can't be avoided that a Lua function call puts return values on the stack.  The LuaStackObject returned by the LuaPlus function call is the first return value.  There may be more.

operator<< understands most Lua types.  The nil type is special, though.  In order to tell LuaPlus a nil should be inserted in the function's argument list, LuaArgNil() must be passed in.

LuaObject funcObj = state->GetGlobal("PrintIt");
LuaCall call = funcObj;
LuaStackObject retObj = call << "String" << LuaArgNil() << LuaRun();

LuaRun() takes an optional argument detailing the number of return values allowed.  By default, multiple return values are allowed.

LuaObject funcObj = state->GetGlobal("ThreeReturnValues");
LuaCall call = funcObj;
LuaStackObject retObj = call << LuaRun(1);  // Only accept one return value.

 

 

 

Metatables(元表)

可以通过 GetMetaTable() 函数获得 Metatable 的 LuaObject

Metatable 作为一个基本类型被共享,详细需要参考下面的 元表增强部分(Metatable Enhancements)部分

 

下面不懂

A metatable can be changed for a LuaObject via the SetMetaTable() function.  If the LuaObject represents a table or userdata, the metatable change is as per standard Lua.  If the LuaObject is a basic type, the metatable is changed for all basic types.