Preface

loadstring = bad

Preface by saying: Using loadstring is essentially never a good idea because it is dangerous. (Allowing a user to enter text to find a part would also allow them to obliterate your place, or save it to somewhere public, etc)

object values = good

Instead of storing a string, just store the object itself. E.g., instead of using "workspace.Part" use just workspace.Part. Then you don't have to do the to string and from string at all.

---

Complexities

There can be some amount of complexity in this problem, from the following concerns:

Names aren't necessarily valid identifiers:

• They can contain punctuation
• They can contain spaces
• They can start with non letters

More than the period is used to identify child names (can be because of the above): * You can use brackets combined with strings * Strings have 3 quote styles * Strings are expressions so technically computation could be in here, but hopefully you don't want that * Periods and brackets are valid characters in names

As far as I know, :GetFullName() ignores these complexities entirely. Thus if a part is named Part.Blah then its :GetFullName() will be game.Workspace.Part.Blah, etc. You have been warned.

---

Simple Solution

• Assumes all names are valid identifiers and do not contain periods
• Periods are the only identifiers for child

In this case, it's a fairly simple problem once we get a string split function. Here is one from the Lua-users Wiki:

function split(self, sep)
        local sep, fields = sep or ":", {};
        local pattern = string.format("([^%s]+)", sep);
        self:gsub(pattern, function(c) fields[#fields+1] = c end);
        return fields;
end

Our first function could look like this:

function getObject(path)
    local obj = {
        game=game,Game=game,
        Workspace=workspace,
        workspace=workspace,
        script=script
    };
    local names = split(path,".");

    for _,name in pairs(names) do
        obj = obj[name];
    end
    return obj;
end

Most of the time, this is enough. If we want to do better...

---

Super Serious Solution

I do a finite state parse and use this to do things like escaping and whatnot after.

Here is the full monster:

function parseStates(text)
    local out = {};
    text = text:sub(text:find("[a-zA-Z_]") ,-1);
    -- Set up states
    local IDENTIFIER = "a";
    local DOUBLE = [["]];
    local SINGLE = [[']];
    local BRACKETS = "{";
    local EBRACKET = ")";
    local BRACKETS1 = "(";
    local INDEX = "[";
    local state = IDENTIFIER;
    -- Set up sub states
    local sub = nil;

    local escaping = false;

    for i = 1,#text do
        out[i] = "?";
        local cs = state;
        local char = text:sub(i,i);
        local remainder = text:sub(i);
        if cs == IDENTIFIER then
            if char:gsub("[a-zA-Z0-9]","") == "" then
                -- Continuation of name
                out[i] = IDENTIFIER;
            else
                if char:gsub("%s","") == "" then
                -- Space: Still identifier (wait for [ or .)
                    out[i] = " ";
                else
                    if char == "." then
                        out[i] = ".";
                        state = IDENTIFIER;
                    elseif char == "[" then
                        state = INDEX;
                        out[i] = "[";
                    else
                        -- Parse error
                        return nil;
                    end
                end
            end
        elseif cs == DOUBLE or cs == SINGLE then
            local escaped = escaping;
            escaping = false;
            out[i] = "x";
            if escaped then
                out[i] = "1";
            else
                local isnum = char:gsub("%d","") == "";
                if out[i-1] == "1" and isnum
                    and text:sub(i-1,i-1):gsub("%d","") == "" then
                    out[i] = "2";
                elseif out[i-1] == "2" and isnum then
                    out[i] = "3";
                else
                    if char == cs then
                        out[i] = state;
                        state = INDEX;
                    elseif char == [[\]] then
                        escaping = i;
                        out[i] = [[\]]
                    end
                end
            end
        elseif cs == EBRACKET then
            out[i] = "}";
            state = INDEX;
        elseif cs == BRACKETS then
            -- Double brackets.
            out[i] = "s";
            if remainder:sub(1,2) == "]]" then
                out[i] = "}";
                state = EBRACKET;
            end
        elseif cs == BRACKETS1 then
            state = BRACKETS;
            out[i] = "{";
        elseif cs == INDEX then
            escaping = false;
            -- *INSIDE* (after) a [
            if char:gsub("%s","") == "" then
                out[i] = " ";
            else
                if remainder:sub(1,2) == "[[" then
                    state = BRACKETS1;
                    out[i] = "{";
                elseif char == "'" or char == '"' then
                    state = char;
                    out[i] = state;
                elseif char == "]" then
                    out[i] = "]";
                    state = IDENTIFIER;
                else
                    -- Parse error
                    print(text);
                    print((" "):rep(i-1) .. "^");
                    return nil;
                end
            end
        end
    end
    return text, table.concat(out,"");
end

function escapes(str,states)
    -- Find numbers in states and combine
    -- them with their backslash (also in states) to make new characters
    local s = "";
    while #str > 0 do
        if states:sub(1,1) == "\\" then
            if states:sub(4,4) == "3" then
                -- "\123"
                local seq = str:sub(2,4);
                s = s .. string.char( tonumber( seq ) );
                states = states:sub(5);
                str = str:sub(5);
            elseif states:sub(3,3) == "2" then
                -- "\12"
                local seq = str:sub(2,3);
                s = s .. string.char( tonumber( seq ) );
                states = states:sub(4);
                str = str:sub(4);
            else
                -- "\1"
                local seq = str:sub(2,2);
                local n = tonumber(seq);
                if n then
                    s = s .. string.char( n );
                else
                    local e = {
                        t="\t", n="\n", r="\r", v="\v", a="\a", b="\b", f="\f"
                    };
                    s = s .. (e[seq] or seq);
                    states = states:sub(3);
                    str = str:sub(3);
                end
            end
        else
            s = s .. str:sub(1,1);
            str = str:sub(2);
            states = states:sub(2);
        end
    end
    return s;
end

function parseStrings(text,states)
    function fits(mode,char)
        if mode == "a" then
            return char == "a";
        end
        if mode == "s" then
            return char == "s";
        end
        if mode == "x" or mode == "\\" then
            return char == "x" or char == "\\" or char == "1"
            or char == "2" or char == "3";
        end
    end
    -- Take adjacent As to turn into a literal string (just copy)
    -- Take adjacent Ss to turn into a literal string (just copy)
    -- Take Xs + 1s + 2s + 3s + \s to escape into a string.
    -- All others are separators
    local t = {};
    local s = "";
    local n = "";
    states = states .. " ";
    text = text .. " ";
    for i = 1, #states do
        if fits(n,states:sub(i,i)) then
            s = s .. text:sub(i,i);
        else
            if s ~= "" then
                if fits("a",n) or fits("s",n) or fits("x",n) then
                    if fits("x",n) then
                        s = escapes(s,states:sub(i-#s,i-1));
                    end
                    table.insert(t,s);
                end
            end
            s = text:sub(i,i);
            n = states:sub(i,i);
        end
    end
    return t;
end

function getNames(text)
    return parseStrings(parseStates(text));
end

function getObject(text,roots)
    local names = getNames(text);
    local obj = roots;
    for i = 1, #names do
        obj = obj[names[i]];
    end
    return obj;
end

---

Usage of this API:

Fully powered parser. Without anything unsafe like loadstring, it fully parses indexing using periods and brackets; it supports all three string types and correct character escaping.

Here is using it to extra a list of names (which is what getObject uses internally):

local text = [[game.Workspace .BlueTaslem["Left\n\tArm"]["Wow"].
Appl37.K ]];
print( text );
print("...");
print( 
        table.concat( getNames(text) , "\n" )
     );
--[[
game.Workspace .BlueTaslem["Left\n\tArm"]["Wow"].
Appl37.K 
...
game
Workspace
BlueTaslem
Left
    Arm
Wow
Appl37
K
]]

And to actually get the object, we use getObject (and pass it all the names that you can start from)

local roots = {};
roots.game = game;
roots.workspace = workspace;
roots.Game = game;
roots.Workspace = Workspace;
roots.script = script;
-- You could also do this so you could
-- get to things like `"table.insert"`:
roots.table = table;

print(getObject("game.Workspace",roots));
--[[
Workspace
]]

Warning It's possible this will result in an error sometimes when you give it an invalid string.

Limitation

I forgot that Lua can use strings delimited by [=[ and ]=] (as in [=[ this is a string [=[ with nested marks ]=] ]=]

This does not support this (and cannot easily because [=[ can be nested).

The good news is I have never seen these used in practice as string literals.