Started work on writing tutorials

Wrote tutorials for
* Setup
* Addon structure
* Inventories
* Items

1 files changed, 30 insertions, 0 deletions

diff --git a/tutorials/tut031_metatables.md b/tutorials/tut031_metatables.md
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+# 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.