what is this code doing?

[gurke93]

In a demo application i read this:

Code: Select all

function Options:update(dt)
	for n,b in pairs(self.button) do
		b:update(dt)
	end
end

and my question ist what does make the "for n,b in pairs [...]". Why i cant write only b:update(dt)? i found this code not only in the update function. For example in the draw function i found it, too.

PLease help!

[Robin]

Well, you need to iterate over the table self.button, which contains tables which have a method called update.

[gurke93]

Oh thanks. Can you explain the funciton in pais for noobs please ?

[Virox]

wel self.button is actually a metatable existing out of keys and values
n = key and b = value (this example a button)

the code itself is a for loop, iterating through every key of the table (in this example every button added to the table)
b:update(dt) <-- this will update the button


Someone correct me if I made mistakes.

[bmelts]

pairs iterates through all of a table's keys. Programming in Lua has more detailed information, in particular, here.

If you want an explanation of how pairs (and its cousin ipairs, which only works on arrays) works, the best resource is probably, again, Programming in Lua. In specific, the section on the generic for.