Mathematica: MTools: Argument Pattern strong type matching does not intrinsically respect inheritance (makes implementing design-by-contract and some Design Patterns less convenient). But you can use PatternTests with Webel MAll extensions.

Whilst argument pattern matching works against a single MTools class name, there is no intrinsic consideration of inheritance. Consider this setup with MClassB extends MClassA:

BeginPackage["Demo`", {"MTools`"}]

$ContextAliases["M`"] = "MTools`Core`MPlusPlus`";

MClassA = M`NewClass[{"Fields"->{"name"}}]

MClassB = M`NewClass[{"Parents"->{MClassA}}]

newB::usage = "newRefR32[name]";

Begin["`Private`"]  

newB[name_] := M`New[MClassB]["name"->name];

End[] 

EndPackage[]

This works as expected (matches against a specific class):

i: b1 = newB["b1"];

i: fTestB[b_MClassB] := M`o.name;

i: fTestB[b1]

o: b1 

But matching against the parent (base) class does not work:

i: fTestA[b_MClassA] := M`o.name;

i: fTestA[b1]

o: fTestA[MClassB[object$123435]]

The Webel MAll MTools extension and All` package provide additional support for more convenient contract tests for use with PatternTest (? queries), as shown in this slide: But it's not so elegant (it would be nicer to have contract matching built-in via a fully vendor supported OO mechanism). Visit also:

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NEW: The Webel recipe for pseudo classes with adapted Abstract Data Types (ADTs) handles design-by-contract fine: