Inheritance

Working with Inheritance Relations in CAEX

This topic contains the following examples:

• Inheritance of SystemUnitClasses
• Overriding inherited elements
• Inheritance relations in role references

Inheritance Relations exist between classes. A Subclass inherits properties from its base class.

The programming examples show how to create inheritance relations between classes and how to use inheritance relations to interpret the meaning of AutomationML objects.

Inheritance of SystemUnitClasses

Inheritance of classes can be defined for SystemUnitFamilyType-,RoleFamilyType-, InterfaceFamilyType- and AttributeFamilyType- elements. This example defines SystemUnitClass inheritance, other classes can be treated in the same way.

using Aml.Engine.CAEX;
using Aml.Engine.CAEX.Extensions;
using Aml.Engine.Services;

void CreateSystemUnitClassInheritance (CAEXDocument document)
{
    // adding a Class library and some classes
    var systemUnitClassLib = document.CAEXFile.SystemUnitClassLib.Append("Slib");
    var suc1 = systemUnitClassLib.SystemUnitClass.Append("s1");
    var suc2 = systemUnitClassLib.SystemUnitClass.Append("s2");
    var suc3 = systemUnitClassLib.SystemUnitClass.Append("s3");
    
    // suc2 becomes a sub class from suc1
    suc2.BaseClass = suc1;

    // suc3 becomes a sub class from suc2
    suc3.BaseClass = suc2;

    // get the inheritance hierarchy from suc3 (the base classes)
    var inheritanceHierarchy = suc3.GetReferenceHierarchy().ToArray();

    Debug.Assert(inheritanceHierarchy[0] == suc3);
    Debug.Assert(inheritanceHierarchy[1] == suc2);
    Debug.Assert(inheritanceHierarchy[2] == suc1);

    // gets the sub classes from suc1 (this also includes the sub-sub classes and further)
    var s = ServiceLocator.QueryService.AllClassReferencesDeep (suc1);

    Debug.Assert(s.Count() == 2);    
}

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Overriding inherited elements

Inherited elements defined in base classes like AttributeType-, InternalElementType- or ExternalInterfaceType- elements can be overridden (modified or deleted) in sub-classes.

using Aml.Engine.CAEX;
using Aml.Engine.CAEX.Extensions;

void CreateOverridenAttributes(CAEXDocument document)
{
    // adding a Class library and some classes
    var systemUnitClassLib = document.CAEXFile.SystemUnitClassLib.Append("Slib2");
    var suc1 = systemUnitClassLib.SystemUnitClass.Append("s1");
    var suc2 = systemUnitClassLib.SystemUnitClass.Append("s2");
    var suc3 = systemUnitClassLib.SystemUnitClass.Append("s3");
    var suc4 = systemUnitClassLib.SystemUnitClass.Append("s4");

    // suc1 is defined a base class of all other classes
    suc2.BaseClass = suc3.BaseClass =  suc4.BaseClass = suc1;

    // adds an attribute to the base class
    var baseAtt = suc1.Attribute.Append("att1");

    // the added attribute is visible in all sub classes
    Debug.Assert(suc2.GetInheritedAttributes().Count() == 1);
    Debug.Assert(suc2.GetInheritedAttributes().First() == baseAtt);

    // this overrides the base class attribute 'att1'
    var overridenAtt = suc3.Attribute.Append("att1");

    // there is still only one attribute in the inheritance tree
    Debug.Assert(suc3.GetInheritedAttributes().Count() == 1);
    Debug.Assert(suc3.GetInheritedAttributes().First() == overridenAtt);

    // this deletes the inherited attribute from s4
    suc4.DeleteInheritedElement("att1", baseAtt.GetType());
    Debug.Assert(suc4.GetInheritedAttributes().Count() == 0);
}

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Inheritance relations in role references

Role references can be added to SystemUnitFamilyType objects and InternalElementType objects. In this example, role references of a SystemUnitClass are checked, if specific RoleClasses are supported, where the RoleClasses build an inheritance tree.

using Aml.Engine.CAEX;
using Aml.Engine.CAEX.Extensions;

void CheckRoleReference (CAEXDocument document)
{
    // adding a SystemUnitClass library and one class
    var systemUnitClassLib = document.CAEXFile.SystemUnitClassLib.Append("Slib3");
    var suc1 = systemUnitClassLib.SystemUnitClass.Append("s1");

    // adding a RoleClass library and some classes with inheritance relations
    var roleClassLib = document.CAEXFile.RoleClassLib.Append("Rlib");
    var role1 = roleClassLib.RoleClass.Append("r1");
    var role2 = roleClassLib.RoleClass.Append("r2");
    var role3 = roleClassLib.RoleClass.Append("r3");

    // role2 is sub-class of role1
    role2.BaseClass = role1;

    // role3 is sub-class of role2
    role3.BaseClass = role2;

    // assign role2 to the SystemUnitClass suc1, the role is added as a SupportedRoleClass
    suc1.AddRoleClassReference(role2);

    // according to the inheritance relation between role1 and role2 the SystemUnitClass owns
    // a derived relation to role1 as well
    var hasSupportedRole = suc1.HasRoleClassReference(role1, regardInheritanceOfRoleClasses: true);
    Debug.Assert(hasSupportedRole);

    // according to the inheritance relation between role2 and role3 the SystemUnitClass can be checked 
    // for support of a generic role of role3, when no direct support of role3 exists.
    var supportsGenericRole = suc1.HasGenericRoleClassReference(role3);
    Debug.Assert(supportsGenericRole);
}    

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