I have a data structure of nested tables that can be N deep. for example
local data = {
[1] = {
[1] = { "stuff" },
[2] = {
[1] = { "stuff" },
[2] = { "more stuff" },
[3] = {
[1] = "deeper stuff"
}
}
}
Now I can reference "deeper stuff" via data[2][3][1] But is there a way that I can store the 2-3-1 as a key so I can reference this data[key] ?
I am storing a set of actions that are transformed and looped over in a denormalised table. I want to be able to reference that this particular action came from a specific point in the original data table. As this is n levels deep is there a dynamic way of writing [2][3][1]...[n]?
You cannot have a single multi-dimensional key. The only way to achieve something like that would be to have some string like "2-3-1" which you then use in an __index metamethod that tranlates it to the separate keys.
setmetatable(data, {
__index = function(t, k)
for index in k:gmatch("%d+") do
-- insert fancier error handling here
if not t then error("attempt to index nil") end
t = rawget(t, tonumber(index))
end
return t
end
})
print(data["2-3-1"]
Alternatively you use a table as key
setmetatable(data, {
__index = function(t, k)
for i,v in ipairs(k) do
if not t then error("attempt to index nil") end
t = rawget(t, v)
end
return t
end
})
print(data[{2,3,1}]
There are of course more ways to implement the table access in __index.
If data is global you could also use load and do something like
local k = string.gsub("1-1-1", "(%d+)%-?", "[%1]")
local element = load("return data .. k")()
But please don't make data global just so you can do this.
Or you write a function that does that without using metamethods as Egor suggested...
Related
I want to be able to access and edit values in a user-generated table, that can have any number of dimensions.
Say, for this nested table,
table = {
'1',
{
'2.1',
'2.2'
},
{
{
'3.1.1',
'3.1.2'
},
'3.2'
},
}
I would have another table that contains a location for the needed data,
loc = {3, 1, 2}
Ideally, what I'd want is to be able to not only access but edit the values in the table, similar to using table[3][1][2] but by utilizing the loc table,
print(table[loc[1]][loc[2]][loc[3]]) --returns 3.1.2
print(table[loc]) --hypothetically something like this that takes each indexed member of the table in order
I also want to be able to edit this table.
table[loc] = {'3.1.2.1', '3.1.2.2'}
I need to be able to edit the global table, so cannot use the methods listed in this reddit thread, and haven't been able to find the right way to use metatables for this yet. I appreciate the help, thanks.
I think you could simply write an additional function for this purpose.
function TreeGetValue (Tree, Location)
local CorrectTree = true
local Index = 1
local Dimensions = #Location
local SubTable = Tree
local Value
-- Find the most deep table according to location
while (CorrectTree and (Index < Dimensions)) do
local IndexedValue = SubTable[Location[Index]]
if (type(IndexedValue) == "table") then
SubTable = IndexedValue
Index = Index + 1
else
CorrectTree = false
end
end
-- Get the last value, regarless of the type
if CorrectTree then
Value = SubTable[Location[Index]]
end
return Value
end
Here, we assume that the tree is well-formatted as the beginning. If we find any problem we set the flag CorrectTree to false in order to stop immediately.
We need to make sure we have a table at every dimension in order index a value from.
> TreeGetValue(table, loc)
3.1.2
Obviously, it's also easy to to write the set function:
function TreeSetValue (Tree, Location, NewValue)
local Index = 1
local Dimensions = #Location
local SubTable = Tree
-- Find the most deep table according to location
while (Index < Dimensions) do
local IndexedValue = SubTable[Location[Index]]
-- Create a new sub-table if necessary
if (IndexedValue == nil) then
IndexedValue = {}
SubTable[Location[Index]] = IndexedValue
end
SubTable = IndexedValue
Index = Index + 1
end
-- Set or replace the previous value
SubTable[Location[Index]] = NewValue
end
And then to test it with your test data:
> TreeGetValue(table, loc)
3.1.2
> TreeSetValue(table, loc, "NEW-VALUE")
> TreeGetValue(table, loc)
NEW-VALUE
I'm new to lua, and I'm having trouble with a basic sort-by-bool-condition thing for entries in a table.
`local tblFormReturn = {
{
['Name'] = 'Spike',
['Year'] = '10',
['House'] = 'Holmes',
['Form Returned'] = true
},
{
['Name'] = 'Elvis',
['Year'] = '11',
['House'] = 'Shaw',
['Form Returned'] = true
},
{
['Name'] = 'Michael',
['Year'] = '10',
['House'] = 'Langley',
['Form Returned'] = false
},
{
['Name'] = 'Chang',
['Year'] = '11',
['House'] = 'Holmes',
['Form Returned'] = false
}
}`
Basically, I want to be able to take this table, and for each chunk, check whether the kid is in Holmes house (1) and if they have returned their form (2). My feeling is I need to run a for-loop in pairs based off the lua manual, but I'm confused as to how I can access these values, given each chunk is sort of a sub-table. My attempts have all been based around something like this.
for i,'Form Returned' in tblFormReturned('Form Returned') do
if 'Form Returned' == true then
if 'House' == 'Holmes' then
print ('Number of Holmes forms returned' +1)
end
end
end
I'm not sure how to make this work. Any help greatly appreciated.
A few things of note here.
When you quote something (indicated by using the single quotes), you effectively make it a string.
A for loop loops through a table using ipairs (indexed pairs, such as yours is) or pairs (used on dictionary tables). Dictionary tables are considered those that are have a defined key rather than an index key (e.g. tblPets = {dog = "Fido", cat = "Sassy", duck = "Quackers} - this would allow you to return tblPets.dog (or tblPets["dog"]) to get the value).
Your print statement to add a number does not work. You cannot add a number to a string. Instead, you will need to set a count as a variable and add to it, provided it is a number.
Lastly, you can also combine the if statements into one to make it easier.
formCount = 0 -- This initializes the variable formCount as an interger, starting with 0.
for i,v in ipairs(tblFormReturned) do -- This iterates through the table
if v["Form Returned"] and v.House == "Holmes" then -- Looks to see if the form returned is true and house is Holmes. Note that with boolean values, you do not have to see if it equals true or false. if v["Form Returned"] == true and this format returns the same answer.
formCount = formCount + 1 -- Adds 1 to the formCount
end -- end if statement
end -- end for loop
Hopefully this helps a little with understanding. If you have any questions, don't hesitate to ask for clarification.
The Issue is I have a dictionary that holds all my data and its supposed to be able to turn into a directorys in replicated storage with all the values being strings then turn back into a dictionary with all the keys when the player leave. However, I cant figure out how to turn into a dictionary(With keys).
ive sat for a few hours testing things but after the first layer of values I cant get figure out a way to get the deeper values and keys into the table
local DataTable =
{
["DontSave_Values"] =
{
["Stamina"] = 100;
};
["DontSave_Debounces"] =
{
};
["TestData"] = 1;
["Ship"] =
{
["Hull"] = "Large_Ship";
["Mast"] = "Iron_Tall";
["Crew"] =
{
["Joe One"] =
{
["Shirt"] = "Blue";
["Pants"] = "Green"
};
["Joe Two"] =
{
["Shirt"] = "Silver";
["Pants"] = "Brown";
["Kids"] =
{
["Joe Mama1"] =
{
["Age"] = 5
};
["Joe Mama2"]=
{
["Age"] = 6
};
}
};
}
};
["Level"] =
{
};
["Exp"] =
{
};
}
------Test to see if its an array
function isArray(Variable)
local Test = pcall(function()
local VarBreak = (Variable.." ")
end)
if Test == false then
return true
else
return false
end
end
------TURNS INTO FOLDERS
function CreateGameDirectory(Player, Data)
local mainFolder = Instance.new("Folder")
mainFolder.Parent = game.ReplicatedStorage
mainFolder.Name = Player.UserId
local function IterateDictionary(Array, mainFolder)
local CurrentDirectory = mainFolder
for i,v in pairs(Array) do
if isArray(v) then
CurrentDirectory = Instance.new("Folder", mainFolder)
CurrentDirectory.Name = i
for o,p in pairs(v) do
if isArray(p) then
local TemporaryDir = Instance.new("Folder", CurrentDirectory)
TemporaryDir.Name = o
IterateDictionary(p, TemporaryDir)
else
local NewValue = Instance.new("StringValue", CurrentDirectory)
NewValue.Name = o
NewValue.Value = p
end
end
else
local value = Instance.new("StringValue", mainFolder)
value.Name = i
value.Value = v
end
end
end
IterateDictionary(Data, mainFolder)
end
------To turn it back into a table
function CreateTable(Player)
local NewDataTable = {}
local Data = RS:FindFirstChild(Player.UserId)
local function DigDeep(newData, pData, ...)
local CurrentDir = newData
for i,v in pairs(pData:GetChildren()) do
if string.sub(v.Name,1,8) ~= "DontSave" then
end
end
end
DigDeep(NewDataTable, Data)
return NewDataTable
end
I expected to when the player leaves run createtable function and turn all the instances in replicated storage back into a dictionary with keys.
Why not just store extra information in your data table to help make it easy to convert back and forth. As an example, why not have your data look like this :
local ExampleData = {
-- hold onto your special "DON'T SAVE" values as simple keys in the table.
DONTSAVE_Values = {
Stamina = 0,
},
-- but every element under ReplicatedStorage will be used to represent an actual Instance.
ReplicatedStorage = {
-- store an array of Child elements rather than another map.
-- This is because Roblox allows you to have multiple children with the same name.
Name = "ReplicatedStorage",
Class = "ReplicatedStorage",
Properties = {},
Children = {
{
Name = "Level",
Class = "NumberValue",
Properties = {
Value = 0,
},
Children = {},
},
{
Name = "Ship",
Class = "Model",
Properties = {},
Children = {
{
-- add all of the other instances following the same pattern :
-- Name, Class, Properties, Children
},
},
},
}, -- end list of Children
}, -- end ReplicatedStorage element
};
You can create this table with a simple recursive function :
-- when given a Roblox instance, generate the dataTable for that element
local function getElementData(targetInstance)
local element = {
Name = targetInstance.Name,
Class = targetInstance.ClassName,
Properties = {},
Children = {},
}
-- add special case logic to pull out specific properties for certain classes
local c = targetInstance.ClassName
if c == "StringValue" then
element.Properties = { Value = targetInstance.Value }
-- elseif c == "ADD MORE CASES HERE" then
else
warn(string.format("Not sure how to parse information for %s", c))
end
-- iterate over the children and populate their data
for i, childInstance in ipairs(targetInstance:GetChildren()) do
table.insert( element.Children, getElementData(childInstance))
end
-- give the data back to the caller
return element
end
-- populate the table
local Data = {
ReplicatedStorage = getElementData(game.ReplicatedStorage)
}
Now Data.ReplicatedStorage.Children should have a data representation of the entire folder. You could even save this entire table as a string by passing it to HttpService:JSONEncode() if you wanted to.
When you're ready to convert these back into instances, use the data you've stored to give you enough information on how to recreate the elements :
local function recreateElement(tableData, parent)
-- special case ReplicatedStorage
if tableData.Class == "ReplicatedStorage" then
-- skip right to the children
for i, child in ipairs(tableData.Children) do
recreateElement(child, parent)
end
-- quick escape from this node
return
end
-- otherwise, just create elements from their data
local element = Instance.new(tableData.Class)
element.Name = tableData.Name
-- set all the saved properties
for k, v in pairs(tableData.Properties) do
element[k] = v
end
-- recreate all of the children of this element
for i, child in ipairs(tableData.Children) do
recreateElement(child, element)
end
-- put the element into the workspace
element.Parent = parent
end
-- populate the ReplicatedStorage from the stored data
recreateElement( Data.ReplicatedStorage, game.ReplicatedStorage)
You should be careful about how and when you choose to save this data. If you are playing a multiplayer game, you should be careful that this kind of logic only updates ReplicatedStorage for the first player to join the server. Otherwise, you run the risk of a player joining and overwriting everything that everyone else has been doing.
Since there isn't a way to iterate over properties of Roblox Instances, you'll have to manually update the getElementData function to properly store the information you care about for each type of object. Hopefully this helps!
If anyone else has this problem the solution I used was just to convert the instances strait into JSON format(I used the names as keys). so that way I can save it, and then when the player rejoins I just used JSONDecode to turn it into the dictionary I needed.
function DirToJSON(Player)
local NewData = RS:FindFirstChild(Player.UserId)
local JSONstring="{"
local function Recurse(Data)
for i, v in pairs(Data:GetChildren()) do
if v:IsA("Folder") then
if #v:GetChildren() < 1 then
if i == #Data:GetChildren()then
JSONstring=JSONstring..'"'..v.Name..'":[]'
else
JSONstring=JSONstring..'"'..v.Name..'":[],'
end
else
JSONstring=JSONstring..'"'..v.Name..'":{'
Recurse(v)
if i == #Data:GetChildren()then
JSONstring=JSONstring..'}'
else
JSONstring=JSONstring..'},'
end
end
else
if i == #Data:GetChildren()then
JSONstring=JSONstring..'"'..v.Name..'":"'..v.Value..'"'
else
JSONstring=JSONstring..'"'..v.Name..'":"'..v.Value..'",'
end
end
end
end
Recurse(NewData)
JSONstring = JSONstring.."}"
return(JSONstring)
end
I have a table and I'm trying to access a specific location that is passed in as a String. What is the easiest way to use the string to access the correct location?
Example, if the table looks like this:
a.b1 = true
a.b2.c1 = true
a.b2.c2 = false
a.b3 = true
How can I change a.b2.c2 to true given a location 'a.b2.c2' as a string.
If you have just a single level, you can use square-brace indexing:
function setSingle(obj, key, value)
obj[key] = value
end
setSingle(a, "b1", "foo")
print(a.b1) --> foo
If you have multiple, you need to do several iterations of this indexing. You can use a loop to do that:
function setMultiple(obj, keys, value)
for i = 1, #keys - 1 do
obj = obj[keys[i]]
end
-- Merely "obj = value" would affect only this local variable
-- (as above in the loop), rather than modify the table.
-- So the last index has to be done separately from the loop:
obj[keys[#keys]] = value
end
setMultiple(a, {"b2", "c1"}, "foo")
print(a.b2.c1) --> foo
You can use string.gmatch to parse a properly formatted list of keys. [^.]+ will match "words" made of non-period symbols:
function parseDots(str)
local keys = {}
for key in str:gmatch "[^.]+" do
table.insert(keys, key)
end
return keys
end
Putting this all together,
setMultiple(a, parseDots("b2.c2"), "foo")
print(a.b2.c2) --> foo
One issue you may run into is that you cannot create new tables with this function; you will have to create the containing table before you can create any keys in it. For example, beforing ading "b4.c3" you would have to add "b4".
You can use loadstring to build the statement you want to execute as a string.
a = { b2 = {} }
a.b1 = true
a.b2.c1 = true
a.b2.c2 = false
a.b3 = true
str = "a.b2.c2"
loadstring(str .. " = true")()
print(a.b2.c2)
I have a table something like this:
table = {milk, butter, cheese} -- without "Quotation marks"
I was searching for a way to check if a given value is in the table or not, and found this:
if table.hasValue(table, milk) == true then ...
but it returns nil, any reason why? (it says .hasValue is invalid) or can I get an alternative to check if value exists in that table? I tried several ways like:
if table.milk == true then ...
if table[milk] == true then ...
All of these returns nil or false.
you can try this
items = {milk=true, butter=true, cheese=true}
if items.milk then
...
end
OR
if items.butter == true then
...
end
A Lua table can act as an array or as an associative array (map).
There is no hasValue, but by using a table as an associative array you can easily implement it efficiently:
local table = {
milk = true,
butter = true,
cheese = true,
}
-- has milk?
if table.milk then
print("Has milk!")
end
if table.rocks then
print("Has rocks!")
end
You have a few options here.
One, is to create a set:
local set = {
foo = true,
bar = true,
baz = true
}
Then you check if either of these are in the table:
if set.bar then
The drawback to this approach is that you won't iterate over it in any specific order (pairs returns items in an arbitrary order).
Another option would be to use a function to check each value in a table. This'll be very slow in large tables, which brings us to back to a modification of the first option: A reverse lookup generator: (This is what I'd recommend doing -- unless your set is static)
local data = {"milk", "butter", "cheese"}
local function reverse(tbl, target)
local target = target or {}
for k, v in pairs(tbl) do
target[v] = k
end
return target
end
local revdata = reverse(data)
print(revdata.cheese, revdata.butter, revdata.milk)
-- Output: 3 2 1
This'll generate a set (with the added bonus of giving you the index where the value was in your original table). You can also put the reverse into the same table as the data was in, but this won't go well with numbers (and it'll be messy if you need to generate the reverse again).
If you write table = {milk=true, butter=true, cheese=true}, then you can use if table.milk == true then ....