How to create a string comparison with xparse's \NewDocumentCommand?

Question

My MWE was created with the help of these two Q&As: 1 and 2.

MWE:

\documentclass{article}
\usepackage{xparse}
\usepackage{xstring}
\usepackage{pdftexcmds}

% Command declaring a global definition if argument not empty, and using a pre-defined empty definition if argument empty
\ExplSyntaxOn%
\NewDocumentCommand{\Client}{g}%
  {%
     \IfNoValueTF{#1}%
      {%
        \tl_use:N \g_jalep_client_tl%
      }%
      {%
        \tl_gset:Nn \g_jalep_client_tl {#1}%
      }%
  }%
\tl_new:N \g_jalep_client_tl%
\ExplSyntaxOff%

% Attempt using \pdfstrcmp 
\makeatletter
\newcommand\foo[1]{%
  \ifnum\pdf@strcmp{\unexpanded{#1}}{Adam}=0 %
     \expandafter\@firstoftwo
  \else
    \expandafter\@secondoftwo
  \fi
    {Adam}
    {Eve}%
}
\makeatother

\begin{document}
\Client{Adam}
% Attempt using xstring
\par My client should be Adam: \IfSubStr{Adam}{\Client}{Adam}{Eve}
% Attempt using \pdfstrcmp
\par My client should be Adam: \foo{\Client}
\end{document}

Output:

Notes:

The \IfSubStr and \foo line work when there exists something like: \newcommand{\Client}{Adam} or \newcommand{\Client}{Eve} or \newcommand{\Client}{Anything}.
From this, I'm inclined to believe \Client produces something other than a string? How do I change this/convert this/work with this when I'm trying to create an if-else statement?

Question:

How do I make a string comparison with the \NewDocumentCommand shown in my MWE? Something like: If \Client = Adam, then print: Adam, else print: Eve

@Werner Yes, though in my document: 1. \Client is always called either empty like this: \Client{} or with any argument like this: \Client{Argument}. 2. \Client{} or \Client{Argument} should print nothing, and only the command \Client should print whatever the global definition defined with \Client is — jed, Jan 16 '19 at 02:05
So, a first call to \Client{<name>} destroys its and just stores the <name>. — Werner, Jan 16 '19 at 02:35

score 1 · Accepted Answer · answered Jan 16 '19 at 16:14

The following doesn't use LaTeX3, but works the way you want it, both using xstring and \pdfstrcmp:

\documentclass{article}

\usepackage{xstring}

\newcommand{\Client}[1]{\renewcommand{\Client}{#1}}

\makeatletter
\newcommand\foo[1]{%
  \ifnum\pdfstrcmp{#1}{Adam}=0 %
     \expandafter\@firstoftwo
  \else
    \expandafter\@secondoftwo
  \fi
  {Adam}
  {Eve}%
}
\makeatother

\begin{document}

\Client{Adam}

% Attempt using xstring
My client should be Adam: \IfSubStr{Adam}{\Client}{Adam}{Eve}

% Attempt using \pdfstrcmp
My client should be Adam: \foo{\Client}

\end{document}

How to create a string comparison with xparse's \NewDocumentCommand?

MWE:

Output:

Notes:

Question:

1 Answers1