Userdata: Difference between revisions
From Legacy Roblox Wiki
Jump to navigationJump to search
>Blocco No edit summary |
>JulienDethurens No edit summary |
||
| (9 intermediate revisions by 6 users not shown) | |||
| Line 1: | Line 1: | ||
A userdata is | ==Userdata== | ||
===What is a userdata?=== | |||
A {{type|userdata}} is the type Lua uses for data structures in the underlying C program. There aren't native Lua functions for handling those types, they must be handled via [[metatables]]. All Roblox objects and events are {{type|userdata}} Lua type. | |||
===Using userdatas=== | |||
You can create a new {{type|userdata}} with an empty metatable by passing true to the undocumented [[newproxy]] function. This {{type|userdata}} cannot be used for anything other than invoking functions via its metatable. | |||
{{Example|<pre> | |||
<pre> | local ud = newproxy(true) -- new userdata with an empty metatable | ||
userdata Foo | getmetatable(ud).__index = {Foo = "Bar"} -- index metamethod | ||
</pre> | print(type(ud), ud.Foo) | ||
[[Category:Data | |||
Output: | |||
userdata: 0x631fc8 Bar | |||
</pre>}} | |||
[[Category:Data types]] | |||
Latest revision as of 17:59, 7 April 2012
Userdata
What is a userdata?
A userdata is the type Lua uses for data structures in the underlying C program. There aren't native Lua functions for handling those types, they must be handled via metatables. All Roblox objects and events are userdata Lua type.
Using userdatas
You can create a new userdata with an empty metatable by passing true to the undocumented newproxy function. This userdata cannot be used for anything other than invoking functions via its metatable.
Example
local ud = newproxy(true) -- new userdata with an empty metatable
getmetatable(ud).__index = {Foo = "Bar"} -- index metamethod
print(type(ud), ud.Foo)
Output:
userdata: 0x631fc8 Bar
