I want to declare a variable in class that takes in the font name from the preamble of the TeX file.
Something like docFont<Variable>. Is there a command that could nullify the space key in latex? For example docFont Arial would return the same result as docFontArial.

My myclass.cls File is something like this:

NeedsTeXFormatLaTeX2e
ProvidesClassmyclass[2019/04/09 Standard HomeWork Template]
LoadClass[a4paper,12pt,onecolumn,final]article
RequirePackgeetoolbox
defhFont#1gdef@hFont#1
def@hFont@latex@warning@no@lineNo noexpandhFont given
BeforeBeginEnvironmentdocument
RequirePackagexepersian
settextfont@hFont

And my *.Tex file is something like this:

documentclassmyclass
hFontArial %Document Persian Font
begindocument
something
enddocument

You can use the trimspaces package for this purpose.

Simple examples

documentclassarticle
usepackagetrimspaces

makeatletter
newcommand*trim[1]%
 trim@spaces@noexp#1%

makeatother

begindocument
textbar trima bcd eftextbar

textbar trim a bcd ef textbar
enddocument

Here is another way that first stores the result of the trimming operation in a macro (my@tmp@trimmed), then expands this macro:

documentclassarticle
usepackagetrimspaces

makeatletter

newcommand*trim[1]%
 begingroup
 edefmy@tmp@trimmedtrim@spaces@noexp#1%
 expandafter
 endgroup
 my@tmp@trimmed


makeatother

begindocument
Xtrima bc defY

Xtrim a bc def Y
enddocument

Overview of the possibilities

The trimspaces package offers several variants depending on what you want:

• left-only, right-only or both-sides trimming (left: trim@pre@space and trim@pre@space@noexp; right: trim@post@space, trim@post@space@noexp; both: trim@spaces, trim@spaces@noexp);


• whether you want to expand tokens while trimming, or not (so far, I chose the @noexp variant in the examples, that just trims without expanding; otherwise, see trim@spaces in the package documentation and below).

It also allows one to trim the contents of an already-existing macro. Here is the example from the documentation concerning this point:

defb b foo ! 
trim@spaces@inb

is equivalent to

defbb foo !

trim@pre@space@in and trim@post@space@in offer analoguous functionality for left-only, resp. right-only trimming.

Difference between trim@spaces and trim@spaces@noexp

The following example illustrates the functional difference between trim@spaces and trim@spaces@noexp¹: the former expands tokens from its argument whereas the latter doesn't (they can then be expanded “at the last moment”, which is often desirable).

documentclassarticle
usepackagetrimspaces

makeatletter
newcommand*storeTrimmedImmediateExp[2]%
 xdef#1trim@spaces#2%


newcommand*storeTrimmedNoExp[2]%
 xdef#1trim@spaces@noexp#2%

makeatother

newcommand*foo[default foo]
storeTrimmedImmediateExpimmediateExp afoo b % foo is expanded now
storeTrimmedNoExpdelayedExp afoo b % foo is not expanded yet
renewcommand*foo[updated foo]


begindocument
textbar immediateExp textbar % there is no foo inside immediateExp

textbar delayedExp textbar % foo is expanded after delayedExp
enddocument

Corner cases

This last example explores a few corner cases with various kinds of spaces:

documentclassarticle
usepackagetrimspaces

makeatletter
newcommand*trim[1]%
 trim@spaces@noexp#1%

makeatother

% Define implicitSpace to be let-equal to a space token
begingroup
 def\globalletimplicitSpace= \ % cf. TeXbook exercise 24.6
endgroup

begindocument
Atrima bc defB

Ctrim a bc def D

Etrim a bc def F % control spaces aren't trimmed

% Implicit space tokens are... sometimes trimmed (?)
GtrimimplicitSpace a bc defimplicitSpaceH
enddocument

Footnote

1. The other difference being that trim@spaces@noexp requires an eTeX engine, while trim@spaces doesn't.

Here, I preprocess the argument to docfont and pass the result to docfontcore, which solely for the purposes of demonstration, detokenizes its argument, so that you can see that it gives the originally specified tokens, trimmed of leading and trailing (but not intermediate) spaces.

The last MWE example shows that passing macros poses no impediment to the approach.

documentclassarticle
usepackage[T1]fontenc
usepackagelistofitems
newcommanddocfont[1]%
 setsepchar!!!!% USE SOMETHING NOT IN THE FONTNAMES
 readlist*trimmedvar#1%
 itemtomacrotrimmedvar[1]thetrimmedvar%
 expandafterdocfontcoreexpandafterthetrimmedvar%

newcommanddocfontcore[1][detokenize#1]
begindocument
docfont Arial Bold 
docfontArial Bold 
docfontArial Bold

newcommandmyfontPalatino
docfont myfont-oblique 
enddocument