5 replies to this topic

[HPWebcamAble]

Ok so lets say I have a 'defualt table'

local defualt = {
  name = "test",
  height = 1,
  width = 1,
  state = true
}

I want to write a function that accepts a table as an arguemnt, then returns that table with all the missing variables filled in from the defualt table

function fillTable(info)
  --#fill in missing stuff
  return info
end

temp = {
  name = "bob"
}

temp = fillTable(temp)

Temp should now be

{
  name = "bob",
  height = 1,
  width = 1,
  state = true
}

How would I go about doing that?

[SquidDev]

I would instinctively do something like:

local merge(a, B)/>
  for k,v in pairs(B)/> do
    a[k] = v
   end
   return a
end
local defaults(a)
  return merge({
    name = "test",
    height = 1,
    width = 1,
    state = true
  }, a)
end

Another way would do it would be this:

local defualt = {
  name = "test",
  height = 1,
  width = 1,
  state = true
}
local defaults(a)
  for k,v in pairs(default)
    if a[k] ~= nil then
	  a[k] = default[k]
    end
  end
  return a
end

[KingofGamesYami]

local defualt = {
  name = "test",
  height = 1,
  width = 1,
  state = true
}

function fillTable( tbl )
  for k, v in pairs( default ) do
    tbl[ k ] = tbl[ k ] or v
  end
  return tbl
end

This will work on everything except boolean inputs, ei state. state will always be set to true unless a non-nil, non-boolean value is in tbl.

Edit:Ninja'd

Edited by KingofGamesYami, 20 February 2015 - 06:56 PM.

[HPWebcamAble]

SquidDev, on 20 February 2015 - 06:56 PM, said:

Spoiler

I would instinctively do something like:

local merge(a, B)/>/>
  for k,v in pairs(B)/>/> do
	a[k] = v
   end
   return a
end
local defaults(a)
  return merge({
	name = "test",
	height = 1,
	width = 1,
	state = true
  }, a)
end

Another way would do it would be this:

local defualt = {
  name = "test",
  height = 1,
  width = 1,
  state = true
}
local defaults(a)
  for k,v in pairs(default)
	if a[k] ~= nil then
	  a[k] = default[k]
	end
  end
  return a
end

KingofGamesYami, on 20 February 2015 - 06:56 PM, said:

Spoiler

local defualt = {
  name = "test",
  height = 1,
  width = 1,
  state = true
}

function fillTable( tbl )
  for k, v in pairs( default ) do
	tbl[ k ] = tbl[ k ] or v
  end
  return tbl
end

This will work on everything except boolean inputs, ei state. state will always be set to true unless a non-nil, non-boolean value is in tbl.

Edit:Ninja'd

Thanks guys

[InDieTasten]

Another way would be to set the __index metamethod to the default table:

function addDefaults(x)
    return setmetatable(x,{__index = defaults})
end

This way every lookup on the table that would end in nil, would be first looked up in the defaults table, and only if theres no entry for the requested index also, it'll return nil, otherwise the default value. It's like prototyping everything in the defaults, if it's not set in the table x and it'll influence x until the metatable is removed/overriden. I consider this somewhat cleaner and your case maybe even faster, as you don't do hell-a-lot of indexing on the returned table. (I would assume it's for your simple button thingy, if i remember correctly)

[HPWebcamAble]

InDieTasten, on 20 February 2015 - 07:40 PM, said:

Another way would be to set the __index metamethod to the default table:

function addDefaults(x)
	return setmetatable(x,{__index = defaults})
end

This way every lookup on the table that would end in nil, would be first looked up in the defaults table, and only if theres no entry for the requested index also, it'll return nil, otherwise the default value. It's like prototyping everything in the defaults, if it's not set in the table x and it'll influence x until the metatable is removed/overriden. I consider this somewhat cleaner and your case maybe even faster, as you don't do hell-a-lot of indexing on the returned table. (I would assume it's for your simple button thingy, if i remember correctly)

You are correct, its for my Screen API.
I think Squid and King's answers pretty much covered what I need, but this is good to know about

Edited by HPWebcamAble, 20 February 2015 - 08:24 PM.