Streamlined String Formatting with Metatables (clean up your display code!)

Lin

Hi! No, I'm not back, but I was scavenging some things from my old system and I come dispensing goodies.

Ever have to write a multi-colored display? It probably looks a little something like this:

cecho("" .. room.name .. ". [" .. room.num .. "] [<" .. getEnvironmentColor(room.env) .. ">" .. getEnvironmentShortName(room.env) .. "] [" .. getCleanAreaName(room.area) .. "]")

Just a complete mess, right? The Lua function string.format() alleviates some of this by using a handy token syntax. It can also be a little bit of a pain though - who wants to wrap every string they write in another nested function?

With a little metatable tweaking, we can create a sort of shorthand for string.format() by hijacking the modulo operator - useful for arithmetic, not so much for strings - and giving it a handler.

---

Add the following somewhere in a high level script:

getmetatable("").__mod = function(a, b)
	if not b then
		return a
  elseif type(b) == "table" then
    return string.format(a, unpack(b))
  else
    return string.format(a, b)
  end
end

---

Now strings have a new behavior. You can use the following format:

"My string, with various %s, %d, and other tokens" % {"a string", 12345}

---

Before, you'd write:

local my_name = "Ben"
local my_age = "twenty"
echo("Hello, my name is " .. my_name .. ". I am " .. my_age .. " years old.")

But now you can do:

local my_name = "Ben"
local my_age = 20
echo("Hello, my name is %s. I am %d years old." % {my_name, my_age})

Although a tiny bit tricky to get used to at first, this new method can greatly save writing time and improve readability. It works anywhere you'd use a string. In addition, string.format() is a highly optimized function implemented in ANSI C, and though most users won't notice a difference, it'll be a little easier on your system where memory usage is concerned.

local my_divine = "The Goddess %s" % {"Iosyne"}

enableTrigger("%s" % {my_trigger})

etc. etc.

And thanks to just how chill Lua is with indenting/linebreaking your functions for readability's sake, you can rewrite that monstrosity at the beginning of this post as...

cecho("%s. [%d] [<%s>%s] [%s]" % {
	room.name, room.num, getEnvironmentColor(room.env), getEnvironmentShortName(room.env), getCleanAreaName(room.area)
	})

Still a lot to track, but damn if it isn't easier to manage.

Enjoy!

Oonagh

EDITED: IM SORRY I DIDNT KNOW.