Add Rows to Table With Macro

Question

I've read the answer given here but haven't been able to modify the code to allow me to insert \hline between each row added to my table.

How can the code by modified to insert \hline each time a new row is defined?

So there would be a line between R1C1 | R1C2 and R2C1 | R2C2 just like there's a line between the headers and the main table contents.

Answer 1

The insertion of \@gobble at the start of \foorows in the linked answer is meant to gobble the first & of the row. You can insert \hline just before that to always insert a horizontal rule with every \addtotable:

\documentclass{article}

\newcommand\foorows{}

\makeatletter
\newcommand\addtotable[1]{%
  \g@addto@macro\foorows{\hline\@gobble}% Insert horizontal rule and gobble first &
  \@for\tmp:=#1\do{%
    \expandafter\g@addto@macro\expandafter\foorows
      \expandafter{\expandafter&\tmp}%
  }%
  \g@addto@macro\foorows{\\}%
}
\makeatother

\begin{document}

\addtotable{R1C1,R1C2,R1C3,R1C4}
\addtotable{R2C1,R2C2,R2C3,R2C4}

\begin{table}[htp]
  \centering
  \begin{tabular}{ |c|c|c|c| }
    \hline
    Header 1 & Header 2 & Header 3 & Header 4 \\ \hline % Header row
    \foorows
    \hline
  \end{tabular}
\end{table}

\end{document}