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Identifier

Description

The Identifier is a construct to identify the class of an object at runtime. All classes derived from OrxonoxClass have an Identifier. The Identifier additionally stores all objects of its class in a list, knows the name of the class, can have a ClassFactory, knows all parents and children, stores config-values, XMLPort-containers, console-commands and provides several other functionalities.

Related classes

Class Identifier

Every Identifier is in fact a ClassIdentifier. Identifier itself is the abstract baseclass of ClassIdentifier. ClassIdentifier is a template. This is needed to take care of the class-specific parts of the Identifier. Read the related Wiki-page for more information.

Subclass Identifier

The SubclassIdentifier is a class, that can act like an Identifier, but has a given base-class. Read the related Wiki-page for more information.

Usage

Identifier of a class

You can get the Identifier of a given class with the macro Class(classname). If you only know the string, so if the class isn't hardcoded, use the macro ClassByString("classname"). You have to include CoreIncludes.h to use the macros.

#include "core/CoreIncludes.h"

// Variant 1:
Identifier* identifierOfMyClass = Class(MyClass);

// Variant 2:
std::string classname = "OtherClass";
Identifier* identifierOfOtherClass = ClassByString(classname);

Identifier of an object

To retrieve the Identifier of an object, use object->getIdentifier():

OrxonoxClass* object = new SomeClass();
Identifier* identifierOfSomeClass = object->getIdentifier();

Name of a class

Use getName():

OrxonoxClass* object = new SomeClass();
object->getIdentifier()->getName(); // returns "SomeClass"

Class(MyClass)->getName(); // returns "MyClass"

New classes

A new class that wants an Identifier must call RegisterObject(classname) in the constructor. A new interface has to inherit virtually from OrxonoxClass and call RegisterRootObject(interfacename) from in the constructor. Both macros are located in CoreIncludes. Read the related Wiki-page for more information.

#include "core/CoreIncludes.h"

// Constructor:
MyClass::MyClass()
{
    RegisterObject(MyClass);
}

Creating an object with fabricate()

You can create an object of a class represented by an Identifier by calling fabricate(). This function creates a new instance and returns a BaseObject pointer.

Important: If you have to cast the BaseObject-pointer to the real class, use dynamic_cast.

Identifier* identifier = Class(MyClass);

// Create an instance of MyClass:
BaseObject* object = identifier->fabricate();

// Cast the pointer from BaseObject to MyClass:
MyClass* object2 = dynamic_cast<MyClass*>(object);

Iterating through existing objects

getObjects() returns a pointer to an ObjectListBase, containing all objects of the class. You can iterate through them with an Iterator:

Identifier* identifier = Class(SomeClass);

Iterator it = identifier->getObjects()->begin();
for (; it != identifier->getObjects()->end(); ++it)
{
    it->callAFunction();
}

Important: If you know at compiletime which class you want to iterate through, use ObjectListIterator, because it's much faster:

ObjectList<SomeClass>::iterator it = ObjectList<SomeClass>::begin();
for (; it != ObjectList<SomeClass>::end(); ++it)
{
    it->callAFunction();
}

Comparison

Different Identifiers can be compared by using functions like isA(...) or isChildOf(...) to retrieve information about the class-hierarchy:

  • myidentifier->isA(other): Compares the Identifier (myidentifier) with another Identifier (other). If myidentifier represents exactly the same or an inheriting class, the function returns true.
  • myidentifier->isExactlyA(other): If myidentifier and other represent both the same class, the function returns true.
  • myidentifier->isChildOf(other): If the class represented by myidentifier is a child of the class represented by other, the function returns true.
  • myidentifier->isDirectChildOf(other): Like isChildOf(...), but the class represented by myidentifier must be inherited directly without other classes between (class myidentifierclass : public otherclass).
  • myidentifier->isParentOf(other): If the class represented by myidentifier is a parent of the class represented by other, meaning the other class is a child, the function returns true.
  • myidentifier->isDirectParentOf(other): Like isParentOf(...), but the class represented by myidentifier must be a direct parent without other classes between (class otherclass : public myidentifierclass).

A more graphical explanation:

Green: If you call comparisonFunction(Class(MyClass)) on a green class, the function returns true.
Red: If you call comparisonFunction(Class(MyClass)) on a red class, the function returns false.

comparisionFunction is either isA, isExactlyA, isChildOf, isDirectChildOf, isParentOf or isDirectParentOf.

isA(MyClass): ParentOfParent | Parent | [MyClass | Child | ChildOfChild]
isExactlyA(MyClass): ParentOfParent | Parent | [MyClass] | Child | ChildOfChild
isChildOf(MyClass): ParentOfParent | Parent | MyClass | [Child | ChildOfChild]
isDirectChildOf(MyClass): ParentOfParent | Parent | MyClass | [Child] | ChildOfChild
isParentOf(MyClass): [ParentOfParent | Parent] | MyClass | Child | ChildOfChild
isDirectParentOf(MyClass): ParentOfParent | [Parent] | MyClass | Child | ChildOfChild

More Functions

Hierarchy: Every Identifier provides sets of all parents and children:

  • getParents()
  • getChildren()
  • getDirectParents()
  • getDirectChildren()

Identifiers: There is also a static map containg all existing Identifiers:

  • Identifier::getIdentifierMap()
  • Identifier::getLowercaseIdentifierMap()

ConfigValues: Every Identifier stores the config-values of the class:

  • getConfigValueMap()
  • getLowercaseConfigValueMap()
  • hasConfigValues()

ConsoleCommands: Also, Identifiers store the console-commands of the class:

  • getConsoleCommandMap()
  • getLowercaseConsoleCommandMap()
  • hasConsoleCommands()

XMLPort Params: The same for XMLPort params:

  • getXMLPortParamMap

XMLPort Objects: And XMLPort objects:

  • getXMLPortObjectMap

Examples

The following examples use the class-tree below.

Identifier* myidentifier = Class(A1);            // Assigns the Identifier of A1

myidentifier->isA(Class(BaseObject));            // returns true
myidentifier->isA(Class(A1));                    // returns true
myidentifier->isA(Class(A1B1));                  // returns false
myidentifier->isA(Class(A2));                    // returns false
Class(A3)->isA(Class(Interface1));               // returns true

Class(A1B1)->isChildOf(Class(BaseObject));       // returns true
Class(A1B1)->isChildOf(Class(A1));               // returns true

Class(A1B1)->isDirectChildOf(Class(BaseObject)); // returns false
Class(A1B1)->isDirectChildOf(Class(A1));         // returns true

// Assigns the Identifier of the class with name "A2"
std::string name = "A2";
Identifier* other = ClassByString(name);
// Creates a new instance of A1
BaseObject* newobject = Class(A1)->fabricate();

// Creates a new instance of A1 and casts it to Interface1
Identifier* myidentifier = Class(A3);
Interface1* newobject = dynamic_cast<Interface1*>(myidentifier->fabricate());

Networking

Because Identifiers use pointers, they are not qualified for networking. It's possible to just send the classname and use the Factory, but this is expensive. That's why there's a network ID.

The network ID is an unsigned integer. You can retrieve an Identifier with a given network ID by using the macro ClassByID(int) (include CoreIncludes.h to use it). It's not determined which network ID belongs to which Identifier. This changes from version to version and from system to system, depending on the number of existing classes and the code executed before main(). So ClassByID(5) might be different on each client. That's why the server has to synchronize the network ID's.

You can retrieve the network ID of an Identifier with getNetworkID().
You can set the network ID of an Identifier with setNetworkID(int).

After changing the network ID of an Identifier to newid, there might be two Identifiers with the ID newid. ClassByID(newid) will then return the changed Identifier and not the old one.

Read the Wiki-page of Factory to get more information about how to iterate through all Identifiers.

Technical information

---to come---