Using a switch to pass an option

Question

I created a switch which is defined iff a new geometry should be twosided. Currently, my code looks like this:

\ifdefined\@TwosideSwitch%
  \typeout{SwitchGiven!}%
  \newgeometry{twoside=true, ...}%
\else%
  \typeout{Undefined!}%
  \newgeometry{twoside=false, ...}%
\fi%

where ... are identical big chunks of options regarding geometry. This works, but for the sake of consistency and beauty, I want it to look more like this:

\someMagicWith{\@TwosideSwitch}%
\newgeometry{\applyTwosideAccordingly, ...}%

I tried:

\ifdefined\@TwosideSwitch%
  \def\@Twoside{true}%
\else%
  \def\@Twoside{false}%
\fi%
\newgeometry{twoside=\@Twoside, ...}%

But apparently geometry hates macros for boolean values. Using the available documentation I discovered a specified "twoside" is implemented as setting two other switches, but that does not work for me either:

\ifdefined\@TwosideSwitch%
  \@twosidetrue\@mparswitchtrue%
\else%
  \@twosidefalse\@mparswitchfalse%
\fi%
\newgeometry{...}%

Any experts here? :)

---

ANSWER:

Beautiful! As @ChristianHupfer pointed out, J.Wright wrote:

As a result, you need to either store both the key and value and pre-expand:

\def\myvariable{valid-key-name=some-valid-input}
\expandafter\KeySettingCommand\expandafter{\myvariable}

So this boils down to

\ifdefined\@TwosideSwitch%
  \def\@Twoside{twoside=true}%
\else%
  \def\@Twoside{twoside=false}%
\fi%
\expandafter\newgeometry%
  \expandafter{\@Twoside, ...}%

or shorter

\def\@Twoside{twoside=false}%
\ifdefined\@TwosideSwitch%
  \def\@Twoside{twoside=true}%
\fi%
\expandafter\newgeometry\expandafter{\@Twoside, ...}%