Building a title block for a class

Question

I am trying to build a class with a title block (using titling) such that the end user enters data into two fields. One variable is sopchaptertitle, and the other is sopchapternumber. I want to then concatenate them, and place the resulting title some distance from the top of the page and centered on the page. This will be followed by some distance of white space and the first section.

It should look something like this:

This is my code:

\NeedsTeXFormat{LaTeX2e}
\ProvidesClass{sop}

% Passes and class options to the underlying article class
\DeclareOption*{\PassOptionsToClass{\CurrentOption}{article}}
\ProcessOptions
\LoadClass{article}

% Redefine the page margins
\RequirePackage[left=1in,right=1in,top=.75in,bottom=.75in]{geometry}

% Modifications to the section titles
\renewcommand*\thesection{\arabic{section}.0}
\renewcommand*\thesubsection{\arabic{section}.\arabic{subsection}}
\renewcommand*\thesubsubsection{\arabic{section}.\arabic{subsection}.\arabic{subsubsection}}

% Title block
\RequirePackage{titling}
\newcommand{\sopchaptertitle}[1]{\newcommand{\thesopchaptertitle}{#1}}
\newcommand{\sopchapternumber}[1]{\newcommand{\thesopchapternumber}{#1}}
\let\oldtitle\title
\renewcommand{\title}[1]{\oldtitle{#1}\newcommand{\mythetitle}{#1}}
\let\oldpretitle\pretitle
\renewcommand{\pretitle}[1]{\oldpretitle{#1}\newcommand{\mythepretitle}{#1}}
\let\oldposttitle\posttitle
\renewcommand{\posttitle}[1]{\oldposttitle{#1}\newcommand{\mytheposttitle}{#1}}
\renewcommand{\maketitle}{%
\mythepretitle{\setlength{\droptitle}{12.0cm}\begin{center}\LARGE}
\mythetitle{\thesopchaptertitle\ \thesopchapternumber}
\mytheposttitle{\par\end{center}\vskip 0.5em}
}
%.... a page N of M section (which works)
% For easier customization of itemized, enumerated, and other lists
\RequirePackage{enumitem}
% For hyperlinked cross-references
\RequirePackage{hyperref}
% Ensure first page is correct style
\thispagestyle{plain}
% That's all, folks!
\endinput

It is being fed this:

\documentclass[10pt]{sop}
%
% SOP Standard Form Data
\sopchaptertitle{This is my procedure title}
\sopchapternumber{this is my procedure number D.4}
%...more of the above
%Here begins the actual document
\begin{document}

\maketitle

\section{Main Title}

\section{Approval}
Approval1....\makebox[1.5in]{\hrulefill}\\\vspace{1.5in}
Approval2....\makebox[1.5in]{\hrulefill}

\newpage

\section{Purpose and Discussion}
%...more of the above...
\end{document}

And I am getting these errors:

(/usr/share/texmf/tex/latex/oberdiek/rerunfilecheck.sty)))
! Missing = inserted for \ifnum.
<to be read again> 
                   M
l.4 \sopchaptertitle
                    {this is my procedure title}
? 
! Missing number, treated as zero.
<to be read again> 
                   M
l.4 \sopchaptertitle
                    {this is my procedure title}
? 

And

(/usr/share/texmf/tex/generic/oberdiek/gettitlestring.sty)) (./sop-test.out)
(./sop-test.out)
! Undefined control sequence.
\HyOrg@maketitle ->\mythepretitle 
                                  {\setlength {\droptitle }{12.0cm}\begin {c...
l.15 

? 
! Extra }, or forgotten \endgroup.
\HyOrg@maketitle ...12.0cm}\begin {center}\LARGE }
                                                   \mythetitle     {\thesopchapt...
    l.15 

? 
! Undefined control sequence.
\HyOrg@maketitle ... {center}\LARGE } \mythetitle 
                                                  {\thesopchaptertitle \ \th...
l.15 

? 
! Undefined control sequence.
\HyOrg@maketitle ...apternumber } \mytheposttitle 
                                                  {\par \end {center}\vskip ...
l.15 

? 
! Missing } inserted.
<inserted text> 
                }
l.15 

? 

The braces seem balanced, and everything but the droptitle seems to work.

Could someone please explain why droptitle is not functioning?

Answer 1

The problem is that \mythepretitle is called without ever being given a definition.

According to the code in sop.cls, you have

\let\oldpretitle\pretitle
\renewcommand{\pretitle}[1]{\oldpretitle{#1}\newcommand{\mythepretitle}{#1}}

but you never do

\pretitle{something}

so \mythepretitle is never defined, although you want to use it in \maketitle.

It's not clear why you want an exact duplicate of \pretitle. In titling.sty we find

\newcommand{\pretitle}[1]{\def\@bspretitle{#1}}

so when used in \maketitle it will use the argument at the right spot, see the definition of \maketitle. But you're redefining \maketitle yourself, so the loading of titling becomes completely useless and using \pretitle instead of \mythepretitle will do nothing.

---

Using the features provided by titling you can achieve your result more easily:

sop.cls

\NeedsTeXFormat{LaTeX2e}
\ProvidesClass{sop}

% Passes and class options to the underlying article class
\DeclareOption*{\PassOptionsToClass{\CurrentOption}{article}}
\ProcessOptions
\LoadClass{article}

% Redefine the page margins
\RequirePackage[left=1in,right=1in,top=.75in,bottom=.75in]{geometry}

% Modifications to the section titles
\renewcommand*\thesection{\arabic{section}.0}
\renewcommand*\thesubsection{\arabic{section}.\arabic{subsection}}
\renewcommand*\thesubsubsection{\arabic{section}.\arabic{subsection}.\arabic{subsubsection}}

% Title block
\RequirePackage{titling}
\newcommand{\sopchaptertitle}[1]{\def\@sopchaptertitle{#1}}
\newcommand{\sopchapternumber}[1]{\def\@sopchapternumber{#1}}

%%% Drop before title
\setlength\droptitle{12cm}

%%% Define the internal variable \@title to be the supplied data
\renewcommand\maketitlehooka{%
  \def\@title{\@sopchaptertitle\ \@sopchapternumber}}

%%% No author field, so \maketitlehookb gobbles what comes after it
\renewcommand\maketitlehookb[1]{}

%%% No date field, so \maketitlehookc gobbles what comes after it
\renewcommand\maketitlehookc[1]{}

%%% Formatting the title
\pretitle{\centering\sffamily\LARGE}

%%% Space after the title
\posttitle{\par\vspace{3cm}}

%%% The rest of the class    

%.... a page N of M section (which works)
% For easier customization of itemized, enumerated, and other lists
\RequirePackage{enumitem}
% For hyperlinked cross-references
\RequirePackage{hyperref}
% Ensure first page is correct style
\thispagestyle{plain}
% That's all, folks!
\endinput

If we use this with your minimal example, we get the following result

Probably the drop should be adjusted, taking into account the top margin, the head height and the head separation. If you want exactly 12cm from the top paper margin, possibly

 \setlength{\droptitle}{\dimexpr 12cm-0.75in-\headheight-\headsep\relax}

is what you need.