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diff --git a/tutorials/tut031_metatables.md b/tutorials/tut031_metatables.md new file mode 100644 index 0000000..a397cc9 --- /dev/null +++ b/tutorials/tut031_metatables.md @@ -0,0 +1,30 @@ +# Tut 0x031 + +## Metatables + +In the last tutorial we saw how to make a simple inventory, but we used a function from Gmod's library that was a bit silly. When we made a copy of our inventory, we used table.Copy() to return a copy seperate to the version in the registry. There's nothing wrong with this, but if you have a lot of fields, and default tables in your inventory, this can get quite costly. There's a simple alternative, lua metatables. + +[Programming in Lua](https://www.lua.org/pil/13.html) does a much better job at explaining metatables than I ever could, so take a look at how they use it. We're not going to use all the features they discuss, just 1: the \_\_index method, to replace the DeSerialize() function from @{tut030_inventories.md}. + + function inv:DeSerialize() + local self_copy = {} + local mt = { + __index = function(table,key) + return self[key] + end + } + setmetatable(self_copy,mt) + local json = util.JSONToTable(data) + for k,v in pairs(json) do + local item_name = v[1] + local item_data = v[2] + local item = item_registry.GetItemFromData(item_name,item_data) + self_copy.items[k] = item + end + for k,v in pair(self_copy.items) do + self_copy.weight = self_copy.weight + v.weight + end + return self_copy + end + +Making this change for our example inventory isn't really a big deal, since we don't have many functions, but it's easy to get to a point where it's beneficial to not copy all the fields of an inventory whenever you need to deserialize it. |