What is wrong with this StringReplace code?

Question

I have this string XXX:ABC. I want to remove XXX: so that the string becomes ABC .

The variable Symbol contains the string XXX:ABC .

The code as follows:

MsgBox, Symbol %Symbol%
SearchText := "XXX:"
ReplaceText := ""
StringReplace, newSymbol, Symbol, SearchText, ReplaceText, ALL 
MsgBox, newSymbol %newSymbol%

From the message box output, newSymbol content is the same as Symbol. Can someone tell me what is wrong with my code?

I am using Autohotkey v1.1.14.03.

Answer 1

For command parameters, you have to distinguish between variable parameters and value parameters. StringReplace for instance has the following argument list:

StringReplace, OutputVar, InputVar, SearchText [, ReplaceText, ReplaceAll?]

The docs say furthermore:

OutputVar: The name of the variable in which to store the result of the replacement process.

InputVar: The name of the variable whose contents will be read from.

SearchText: The string to search for.

As you can see, some parameters are expected to be variable names, whereas others are expected to be values like strings or numbers. You can use variable contents as value parameters by either enclosing them in percent signs or using them within an expression:

StringReplace, newSymbol, Symbol, %SearchText%, %ReplaceText%, ALL
; or as an expression
StringReplace, newSymbol, Symbol, % SearchText, % ReplaceText, ALL

Answer 2

With the newer StrReplace() function I noticed I could not use it with variables for whatever reason. And the documentation here: https://autohotkey.com/docs/commands/StringReplace.htm is lacking an example. After a lot of tests, couldn't figure it out. So I wrote a "polyfill" for StrReplace, complete with test code.

; Author: John Mark Isaac Madison
; EMAIL : [e-mail]
; I_SRC : input source text
; I_OLD : old token to find
; I_NEW : new token to replace old with
FN_POLYFILL_STR_REPLACE(I_SRC, I_OLD, I_NEW)
{
    ;Check length of input parameters:
    ;--------------------------------------------;
    L1 := StrLen(I_SRC)
    L2 := StrLen(I_OLD)
    L3 := StrLen(I_NEW)
    if( !(L1 > 0)  )
    {
        msgbox BAD_PARAM_#1:STR_REP
    }
    if( !(L2 > 0)  )
    {
        msgbox BAD_PARAM_#2:STR_REP
    }
    if( !(L3 > 0)  )
    {
        msgbox BAD_PARAM_#3:STR_REP
    }
    ;--------------------------------------------;


    OP := "" ;output string

    f_ptr := 0 ;fill pointer
    max_i := StrLen(I_SRC)
    dx := 0 ;<--Loop counter / index
    LOOP  ;;[LOOP_START];;
    {
        dx++
        if(dx > max_i)
        {
            break ;[BAIL_OUT_OF_LOOP]
        }

        h := FN_IS_TOKEN_HERE(I_SRC, I_OLD, dx)

        ;if(8==dx)
        ;{
        ;    msgbox, HACK_8 dx[%dx%]  h[%h%] I_SRC[%I_SRC%]  I_OLD[%I_OLD%]
        ;    src_len := StrLen( I_SRC )
        ;    old_len := StrLen( I_OLD )
        ;    msgbox src_len [%src_len%]  old_len[%old_len%] I_OLD[%I_OLD%]
        ;}

        if( h > 0)
        {
            ;token found, replace it by concating
            ;the I_NEW onto output string:
            OP := OP . I_NEW
            ;OP := OP . "[X]"

            ;msgbox : I_SRC[%I_SRC%]  h[%h%]  dx[%dx%]

            ;jump pointer to last character of
            ;the found token to skip over
            ;now irrelevant characters:
            dx := h

            ;msgbox, DX: %dx%
        }
        else
        if( 0 == h)
        {
            msgbox, "H_SHOULD_NOT_BE_ZERO"
        }
        else
        if( h < 0 )
        {
            ;concat character to output:
            c := SubStr(I_SRC,dx,1)
            OP := OP . c
        }

    }     ;;[LOOP_END];;


    msgbox OP : %OP%
    ;msgbox I_SRC[ %I_SRC%] I_OLD[ %I_OLD%] I_NEW[ %I_NEW%]
    return OP ;;<--return output string

}


;Author: John Mark Isaac Madison
;EMAIL : [e-mail]
;unit-test that will run when script boots up:
FN_POLYFILL_STR_REPLACE_TEST()
{
    T1 := FN_POLYFILL_STR_REPLACE("WHAT_IS_UP","UP","DOWN")
    ;;msgbox, T1 : %T1%

    i_src := "123_TOKEN_123"
    i_old := "TOKEN"
    i_new := "NEEEW"
    T2  := FN_POLYFILL_STR_REPLACE(i_src,i_old,i_new)
    ;;msgbox, T2 : %T2%

    ;;msgbox, "POLYFILL_TEST_RAN"


    i_src := "const IS_VARNAME"
    i_old := "VARNAME"
    i_new := "BASH"
    T3  := FN_POLYFILL_STR_REPLACE(i_src,i_old,i_new)
    ;msgbox, T3 : %T3%

    i_src := "123456VARNAME"
    i_old := "VARNAME"
    i_new := "AB"
    T4  := FN_POLYFILL_STR_REPLACE(i_src,i_old,i_new)

    if(T1 != "WHAT_IS_DOWN")
    {
        msgbox [PSR_TEST_FAIL#1]
    }

    if(T2 != "123_NEEEW_123")
    {
        msgbox [PSR_TEST_FAIL#2]
    }

    if(T3 != "const IS_BASH")
    {
        msgbox [PSR_TEST_FAIL#3]
    }

    if(T4 != "123456AB")
    {
        msgbox [PSR_TEST_FAIL#4]
    }


    return ;rrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr;
}
FN_POLYFILL_STR_REPLACE_TEST()

Also, be aware that trimming out newlines in your data is harder than it should be as well. And will be bound to throw a monkey wrench into whatever string parsing you are doing.