How to extend string builtins

[yuin]

How to extend string builtins

[otm]

For reference:

func decorateStringLib(L *lua.LState) {
    strlib := L.GetGlobal("string")
    if strlib, ok := strlib.(*lua.LTable); ok {
        index := strlib.RawGetString("__index")
        if index, ok := index.(*lua.LTable); ok {
            index.RawSetString("upper", L.NewClosure(upper))
        }
    }
}

func upper(L *lua.LState) int {
    str := L.CheckString(1)
    str = strings.ToUpper(str)
    L.Push(lua.LString(str))

    return 1
}

In Lua:

str = "banana"
str:upper()

[otm]

To answer my entire question

func decorateStringLib(L *lua.LState) {
    strlib := L.GetGlobal("string")
    if strlib, ok := strlib.(*lua.LTable); ok {
        index := strlib.RawGetString("__index")
        if index, ok := index.(*lua.LTable); ok {
            index.RawSetString("split", L.NewClosure(split))
        }
    }
}

func split(L *lua.LState) int {
    s := L.CheckString(1)
    sep := L.CheckString(2)
    parts := strings.Split(s, sep)

    if L.GetTop() == 3 {
        fn := L.CheckFunction(3)
        p := lua.P{Fn: fn, NRet: 0, Protect: true}
        for i, str := range parts {
            if err := L.CallByParam(p, lua.LString(str), lua.LNumber(i)); err != nil {
                emitFatal("%v", err)
            }
        }
    }

    i := 0
    iterator := func(L *lua.LState) int {
        if i == len(parts) {
            return 0
        }

        L.Push(lua.LString(parts[i]))
        L.Push(lua.LNumber(i))
        i++
        return 2
    }

    L.Push(L.NewClosure(iterator))
    return 1
}

Can be called in Lua by:

    out = "first\nsecond"
    for line in out:split("\n") do
        print("i", line)
    end

    out:split("\n", function(line)
        print("cb", line)
    end)

[yuin]

Or you can do like this:

local mt = getmetatable('')
function mt:print()
   print(self)
end

x = 'hello'
x:print()

[otm]

Thanks! Using GetMetatable made the implementation in Go much simpler

mt := L.GetMetatable(lua.LString("")).(*lua.LTable)
mt.RawSetString("split", L.NewClosure(split))