The macros setmainfont and setsansfont do not accept the new command of a newfontfamily. Is there compatibility between them?

Question

I use the class memoir, the packages polyglossia, fontspec, compile in XeLaTeX in Linux and on macOS.

Based on XeTeX package fontspec: Use previously defined \newfontfamily with \setmainfont (there were not available answers to this), I would like to set an extra font coming from a new command of newfontfamily to setmainfont and setsansfont because I find unnecessary to multiply the same path/localization of the fonts in each macro. I want to economise and optimise the codes. Here is the MWE:

\documentclass[12pt, a4paper, oneside, oldfontcommands, dvipsname]{memoir}

\usepackage{fontspec}

\newfontfamily\alegreya{Alegreya}[Path = ./fontes/,
  FontFace = {xb}{n}  {* Black},
  FontFace = {xb}{it} {* Black Italic},
  UprightFont = * Regular,
  ItalicFont = * Regular Italic,
  BoldFont = * Bold,
  BoldItalicFont = * Bold Italic,
]

\setmainfont{\alegreya}
\setsansfont{\alegreya}

Only my newfontfamily part works, but the set*font does accept the defined newcommand.

Answer 1

You can do it by assigning the family name. The string is essentially arbitrary, so long as it doesn't refer to an existing font family.

(I had to adapt the font setup to my machine.)

\documentclass{article}

\usepackage{fontspec}

\newfontfamily\alegreya{Alegreya}[
  %Path = ./fontes/,
  FontFace = {xb}{n}  {*-Black},
  FontFace = {xb}{it} {*-BlackItalic},
  UprightFont = *-Regular,
  ItalicFont = *-Italic,
  BoldFont = *-Bold,
  BoldItalicFont = *-BoldItalic,
  NFSSFamily=alegreyaot
]

\renewcommand{\rmdefault}{alegreyaot}
\renewcommand{\sfdefault}{alegreyaot}

\begin{document}

This should be Alegreya

\textsf{This too}

{\normalfont\alegreya Check}

\end{document}