Lua: Calling c method that returns userdata to Lua

Im using LuaObjcBridge and I'm calling a method from Lua like this:

local position = owner:position()

In objective-c this returns a CGPoint struct with X and Y which the bridge converts into Userdata. So CGPoint struct -> Lua userdata. In Lua how would I access the X and Y 开发者_JAVA百科values from the Userdata?

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you need to:

• define metatable, that contains methods that operate on userdata
• set metatable on userdata
• set the same metatable as __index field on userdata

or:

• set some methods that operate on userdata
• expose them to Lua

look at http://www.lua.org/pil/28.1.html

userdata can't do anything by itself, you need to add methods that do something with it.