Lua StringBuilder OO Concept

[unityconstruct]

StringBuilder OO Concept

been missing my StringBuilders from C# & Java, so rolling my own Lua one

--- @class StringBuilder
local StringBuilder = {}
--- StringBuilder utility class for manipulating strings
--- @param firstString? string
--- @param isStrictTyping? boolean
--- @return StringBuilder string
function StringBuilder:new(firstString, isStrictTyping)
    self._firstString = firstString or ""
    setmetatable({},self)
    self.__index = self
    --- @type string private field holding the official string value
    self.value = self._firstString
    --- @type boolean flag to enable exception raised if a value other than string/number/boolean/integer attempted
    self._isStrictTyping = isStrictTyping or false

    do   --[[ core functions --]]

        --- return length of the StringBuilder
        --- @return integer length currenty length of the StringBuilder
        self.length = function() return #self.value
        end

        --- append string on same line
        --- @param appendString any
        --- @return StringBuilder StringBuilder
        self.append     = function(appendString)
            self.value     =  string.format("%s%s",self.value,self.typeCast(appendString))
            return self
        end

        --- append string to newline
        --- @param appendString any
        --- @return StringBuilder stringBuilder
        self.appendLine = function(appendString)   self.value =  string.format("%s\n%s",self.value,self.typeCast(appendString))
            return self
        end

        --- prepend the first line of the StringBuilder
        --- @param prependString any
        --- @return StringBuilder
        self.prepend     = function(prependString) self.value = string.format("%s%s",self.typeCast(prependString),self.value)
            return self
        end

        --- prepend the the StringBuilder, inserting newline
        --- @param prependString any
        --- @return StringBuilder
        self.prependLine = function(prependString) self.value = string.format("%s\n%s",self.typeCast(prependString),self.value)
            return self
        end

        --- clear the value of the StringBuilder. Results in empty string
        --- @return StringBuilder
        self.clear = function() self.value = ""
            return self
        end

    end


    do    --[[ utilities --]]

        --- return a linebreak using a character specifying length
        --- @param char string
        --- @param length integer
        --- @return string linebreak 
        function self.linebreaker(char,length)
            local line = char or ""
            -- if (isNull(char) or isNull(length)) then return "" end      -- error checking
            for i=1,length do
                line = line .. char     -- append character
            end
            return line.."\n"           -- add newline at the end
        end

        --- return one or more line feeds
        --- @param lineFeedCount integer
        --- @return string one of more linefeeds ("\n")
        function self.addLines(lineFeedCount)
            local line = ""
            for i=0,lineFeedCount do line = (line .. "\n") end ; return line
        end

        --- helper function to manage `isStrictTyping`, `isTypeSafe` and the built-in tostring() typeCasting
        --- - isStrictTyping
        --- - | true : throw error if type is NOT {string,number,boolean,integer} 
        --- - | false: let tostring() manage the typecasting 
        --- @param value any
        --- @return string typeCasted string
        self.typeCast = function(value)
            local t = type(value)                                                               -- get data type
            local isTypeSafe = false
            if(not self._isStrictTyping and type == "nil" ) then value = ""                          -- handle nil gracefully if string typeing = false
            elseif( t == "string" or t == "number" or t == "boolean" or t == "integer") then    -- check for happy typecasting
                    isTypeSafe = true                                                           -- check if value is type safe
            elseif (self._isStrictTyping and not isTypeSafe) then                                    -- if not & StrictTyping is enabled, throw error
                local msg = string.format("StringTyping is enabled and value passed is not Type-Safe(string/number/boolean):[%s]",t)
                error(msg,-1)                                                                   -- throw error
            end
            return tostring(value)                                                              -- otherwise let tostring() come up with whatever it wants
        end

    end

    return self
end

--- Excercises the StringBuilder Class
local function StringBuilderTests()
    -- instantiate an object from the class WITHOUT passing a value to the constructor
    local stringBuilder = StringBuilder:new()
    local result
    -- output a linebreak to console
    print( StringBuilder.linebreaker("=", 30)    )

    -- instantiate an object from the class WITH passing a value to the constructor
    result = StringBuilder:new("--**INIT VALUE**--")

    -- example of granular use of the Class' functions
    result.append("<<<not a new line>>>")
    result.appendLine("====I'm a new line====")
    print(result.value)
    result.appendLine("__3..2..1..0!!! numbers might be working!!!!___")
    result.appendLine("^^^BooHooHoolean if they are not^^^")
    result.append(true)
    result.prepend("******CUTTING IN FRONT YO!******")
    result.prepend("__ [1] just cut in line now__") ; result.prepend(1)

    -- add linefeeds
    print(StringBuilder.addLines(2))
    -- linebreak with *'s'
    print( StringBuilder.linebreaker("*", 30)    )
    -- more linefeeds
    print(StringBuilder.addLines(2))

    -- clear and verify value reset to ""
    print("1: SB LineByLine ------------------------------")
    print(StringBuilder.addLines(2))
    print(result.value)
    result.clear()
    print(result.value)
    print("1: SB LineByLine ------------------------------")

    -- multi char linebreak 
    print( StringBuilder.linebreaker("=**=", 30)    )
    print(StringBuilder.addLines(5))
    -- easteregg
    print( StringBuilder.linebreaker("______╭∩╮(>_<)╭∩╮ ____", 4)    )

    -- example of function 'chaining'
    result = StringBuilder:new("FRESH").append("[new text on same line]").appendLine("[new text on new line]").prependLine("").prependLine("Inserted text at firstline")


    print("2: VALUE --------------------------------------")
    print(string.format("Result: \n :[%s]",result.value))
    result.clear()
    print(StringBuilder.addLines(5))
    print("2: VALUE --------------------------------------")

    print("3: CLEAR --------------------------------------")
    print(string.format("Result: \n :[%s]",result.value))
    print(StringBuilder:new().linebreaker("=", 30))
    print("3: CLEAR --------------------------------------")
    -- caller:
    -- StringBuilderTests()
end

StringBuilderTests()  -- call tests

*******************************





1: SB LineByLine ------------------------------




1__ [1] just cut in line now__******CUTTING IN FRONT YO!******--**INIT VALUE**--<<<not a new line>>>
====I'm a new line====
__3..2..1..0!!! numbers might be working!!!!___
^^^BooHooHoolean if they are not^^^true

1: SB LineByLine ------------------------------
=**==**==**==**==**==**==**==**==**==**==**==**==**==**==**==**==**==**==**==**==**==**==**==**==**==**==**==**==**==**==**=








______╭∩╮(>_<)╭∩╮ __________╭∩╮(>_<)╭∩╮ __________╭∩╮(>_<)╭∩╮ __________╭∩╮(>_<)╭∩╮ __________╭∩╮(>_<)╭∩╮ ____

2: VALUE --------------------------------------
Result: 
 :[Inserted text at firstline

FRESH[new text on same line]
[new text on new line]]







2: VALUE --------------------------------------
3: CLEAR --------------------------------------
Result: 
 :[]
===============================

3: CLEAR --------------------------------------

[dnaldoog]

You could also do this: :)

        function self.linebreaker(char,length)
            local char = char or ""
           return string.rep(char,length).."\n"
        end

[dnaldoog]

I think the parameter isStrictTyping is unnecessary because type in self.typeCast method is sufficient to determine if the passed object is not amenable to tostring :

… so in the constructor, you would just need:

function StringBuilder:new(firstString)
    self._firstString = firstString or ""
    setmetatable({}, self)
    self.__index = self
    --- @type string private field holding the official string value
    self.value = self._firstString
    --- @type boolean flag to enable exception raised if a value other than string/number/boolean/integer attempted
    do
        --[[ core functions --]]
        --- return length of the StringBuilder
        --- @return integer length currenty length of the StringBuilder
        self.length = function()
            return #self.value
        end

---

 self.typeCast = function(value)
            local t = type(value)
            --[[
            There are eight basic types in Lua: nil, boolean, number, string, userdata, function, thread, and table. 
            The type function gives the type name of a given value:
    print(type("Hello world"))  --> string
    print(type(10.4*3))         --> number
    print(type(print))          --> function
    print(type(type))           --> function
    print(type(true))           --> boolean
    print(type(nil))            --> nil
    print(type(type(X)))        --> string
            ]]
            local isNotTypeSafe = true
            if t == "string" or t == "number" or t == "boolean" or t == "integer" then
                isNotTypeSafe = false
            end
            if isNotTypeSafe then -- throw error
                local msg =
                    string.format(
                    "StringTyping is enabled and value passed is not Type-Safe(string/number/boolean):[%s]",
                    t
                )
                error(msg, -1) -- throw error
            end
            return tostring(value) -- tostring coverts boolean to string false/true                                                    -- otherwise let tostring() come up with whatever it wants
        end
    end

    return self
end

😊

[unityconstruct]

lol... just saw this in my email and was 'what is he talking about typecasting for....' and wouldn't ya know its right there in that class I made. I forget the line of thought on it, but think it was either born out of EXTREME paranoia with crashing Ctrlr.... or there might have been something I saw on diff lua versions. Last few weeks has been a blur while working on my EMU panel. SysexDumps to/from was an interesting experience, but actually working now.

BTW: stole your snippet from earlier this week :)... actually have a TON of your stuff off the off Ctlr.org site that has been immensely helpful with moving things along. So THANKS for all those elder posts.

speaking of types.. figured I'd drop some syntactic funcs for type testing. Almost more typing, but VSCode intellisense does most the work.

    do  --is

        function self.isBoolean(o)          local result = (type(o) == "boolean")          p("isBoolean(o): "       ..tostring(result)) return result end
        function self.isFunction(o)         local result = (type(o) == "function")         p("isFunction(o): "      ..tostring(result)) return result end
        function self.isInteger(o)          local result = (type(o) == "integer")          p("isInteger(o): "       ..tostring(result)) return result end
        function self.isNull(o)             local result = (type(o) == nil)                p("isNull(o): "          ..tostring(result)) return result end
        function self.isNullOrEmpty(o)      local result = (type(o) == nil) or  (o == "")  p("isNullOrEmpty(o):"    ..tostring(result)) return result end
        function self.isNumber(o)           local result = (type(o) == "number")           p("isNumber(o): "        ..tostring(result)) return result end
        function self.isString(o)           local result = (type(o) == "string")           p("isString(o): "        ..tostring(result)) return result end
        function self.isTable(o)            local result = (type(o) == "table")            p("isTable(o): "         ..tostring(result)) return result end
        function self.isUserData(o)         local result = (type(o) == "userdata")         p("isUserData(o): "      ..tostring(result)) return result end
        function self.isNotBoolean(o)       local result = (type(o) ~= "boolean")          p("isNotBoolean(o): "    ..tostring(result)) return result end
        function self.isNotFunction(o)      local result = (type(o) ~= "function")         p("isNotFunction(o): "   ..tostring(result)) return result end
        function self.isNotInteger(o)       local result = (type(o) ~= "integer")          p("isNotInteger(o): "    ..tostring(result)) return result end
        function self.isNotNull(o)          local result = (type(o) ~= nil)                p("isNotNull(o): "       ..tostring(result)) return result end
        function self.isNotNullOrEmpty(o)   local result = (type(o) ~= nil) or (o ~= "")   p("isNotNullOrEmpty(o): "..tostring(result)) return result end
        function self.isNotNumber(o)        local result = (type(o) ~= "number")           p("isNotNumber(o): "     ..tostring(result)) return result end
        function self.isNotString(o)        local result = (type(o) ~= "string")           p("isNotString(o): "     ..tostring(result)) return result end
        function self.isNotTable(o)         local result = (type(o) ~= "table")            p("isNotTable(o): "      ..tostring(result)) return result end
        function self.isNotUserData(o)      local result = (type(o) ~= "userdata")         p("isNotUserData(o): "   ..tostring(result)) return result end

    end

Usage:

    ---Get Component Name
    ---@param comp CtrlrComponent
    ---@return string name
    function UiHandler:GetCompName(comp)
        if(DU.isNotNull(comp))then
            local name = L(comp:getOwner():getName())
            p("GetName: "..name)
            return name
        else
            return ""
        end
    end

[dnaldoog]

Thank you!

All those posts I made my back, it was usually a case of me learning as I wrote. So, a lot of it I would probably change now. But, it’s really the best way to learn something more deeply. 🙏