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Creating a system

Our object manager will in turn be an object called ChemicalSystem , this time built according to the symbol interface method

$ChemicalSystems=1;
ChemicalSystem~SetAttributes~HoldFirst;
$DefaultChemicalSystem:=ChemicalSystem[];

ChemicalSystem[]:=(
 $DefaultChemicalSystem=
 With[{ID=$ChemicalSystems++},
  With[{system=Symbol["ChemicalSystem$"<>ToString@ID]},
   system=<|
    "ID"->ID,
    "Index"->1|>;
    ChemicalSystem[system]
    ]
   ]);
 ChemicalSystem[ID_Integer]:=With[{c=Names@Evaluate["ChemicalSystem$"<>ToString@ID]},
  If[Length@c>0,
   ToExpression[First@c,StandardForm,ChemicalSystem]
   ]
  ]

We’ll reset a default system every time a new system is made so that this system can be used by functions by default.