RWCollectable Class Reference
[RWCollectable-derived]

Contains virtual functions for identifying, hashing, comparing, storing and retrieving collectable objects. More...

#include <rw/collect.h>

Inheritance diagram for RWCollectable:

List of all members.

Public Member Functions
virtual RWCollectable *	newSpecies () const
virtual RWClassID	isA () const
virtual	~RWCollectable ()
virtual RWspace	binaryStoreSize () const
virtual int	compareTo (const RWCollectable *) const
virtual unsigned	hash () const
virtual bool	isEqual (const RWCollectable *t) const
virtual void	restoreGuts (RWFile &)
virtual void	restoreGuts (RWvistream &)
virtual void	saveGuts (RWFile &) const
virtual void	saveGuts (RWvostream &) const
RWspace	recursiveStoreSize () const
RWStringID	stringID () const
Static Public Member Functions
static RWClassID	classIsA ()
static RWspace	nilStoreSize ()
static RWClassID	classID (const RWStringID &name)
static bool	isAtom (RWClassID id)
Friends
RWvistream &	operator>> (RWvistream &s, RWCollectable *&pCl)
RWFile &	operator>> (RWFile &f, RWCollectable *&pCl)
RWvostream &	operator<< (RWvostream &v, const RWCollectable &obj)
RWFile &	operator<< (RWFile &f, const RWCollectable &obj)
RWvistream &	operator>> (RWvistream &v, RWCollectable &obj)
RWFile &	operator>> (RWFile &f, RWCollectable &obj)

---

Detailed Description

Class RWCollectable is an abstract base class for collectable objects. This class contains virtual functions for identifying, hashing, comparing, storing and retrieving collectable objects. While these virtual functions have simple default definitions, objects that inherit this base class typically redefine one or more of them.

Synopsis

 typedef RWCollectable Object;  // Smalltalk typedef
 #include <rw/collect.h>

Persistence

Polymorphic

---

Constructor & Destructor Documentation

virtual RWCollectable::~RWCollectable

(

)

[virtual]

All functions that inherit class RWCollectable have virtual destructors. This allows them to be deleted by such member functions as removeAndDestroy() without knowing their type.

---

Member Function Documentation

virtual RWspace RWCollectable::binaryStoreSize

(

)

const [virtual]

Returns the number of bytes used by the virtual function saveGuts(RWFile&) to store an object. Typically, this involves adding up the space required to store all primitives, plus the results of calling recursiveStoreSize() for all objects inheriting from RWCollectable. See the Essential Tools Module User's Guide for details.

Reimplemented in RWCollection, RWCollectableAssociation, RWCollectableDate, RWCollectableInt, RWCollectableString, RWCollectableWString, RWCollectableTime, RWDBBlob, RWDBValue, and RWCollectableDateTime.

static RWClassID RWCollectable::classID

(

const RWStringID &

name

)

[inline, static]

Returns the result of looking up the RWClassID associated with name in the global RWFactory.

static RWClassID RWCollectable::classIsA

(

)

[static]

Returns the RWClassID of this class.

Reimplemented in RWBinaryTree, RWBTreeDictionary, RWBTree, RWCollectableAssociation, RWCollectableDate, RWCollectableInt, RWCollectableString, RWCollectableWString, RWCollectableTime, RWDBBlob, RWDBRow, RWDBValue, RWDlistCollectables, RWHashDictionary, RWHashTable, RWIdentityDictionary, RWIdentitySet, RWOrdered, RWSlistCollectablesQueue, RWBag, RWSet, RWSlistCollectables, RWSortedVector, RWSlistCollectablesStack, and RWCollectableDateTime.

virtual int RWCollectable::compareTo

(

const RWCollectable *

)

const [virtual]

The function compareTo() is necessary to sort the items in a collection. If p1 and p2 are pointers to RWCollectable objects, the statement:

 p1->compareTo(p2);

should return:

0 if *p1 "is equal to" *p2;

>0 if *p1 is "larger" than *p2;

<0 if *p1 is "smaller" than *p2.

Note that the meaning of "is equal to," "larger" and "smaller" is left to the user. The default definition provided by the base class is based on the addresses, i.e.,

 return this == p2 ? 0 : (this > p2 ? 1 : -1);

and is probably not very useful.

Reimplemented in RWCollectableAssociation, RWCollectableDate, RWCollectableInt, RWCollectableString, RWCollectableWString, RWCollectableTime, RWDBBlob, RWDBValue, and RWCollectableDateTime.

virtual unsigned RWCollectable::hash

(

)

const [virtual]

Returns a hash value. This function is necessary for collection classes that use hash table look-up. The default definition provided by the base class hashes the object's address:

 return (unsigned)this;

It is important that the hash value be the same for all objects that return true to isEqual().

Reimplemented in RWCollectableAssociation, RWCollectableDate, RWCollectableInt, RWCollectableString, RWCollectableWString, RWCollectableTime, RWDBBlob, RWDBCollectableExpr, RWDBValue, and RWCollectableDateTime.

virtual RWClassID RWCollectable::isA

(

)

const [virtual]

Returns a class identification number (with a typedef of unsigned short). The default definition returns __RWCOLLECTABLE. Identification numbers greater than or equal to 0x8000 (hex) are reserved for Rogue Wave objects. User-defined classes should define isA() to return a number between 0 and 0x7FFF.

Reimplemented in RWBinaryTree, RWBTreeDictionary, RWBTree, RWCollection, RWCollectableAssociation, RWCollectableDate, RWCollectableInt, RWCollectableString, RWCollectableWString, RWCollectableTime, RWDBBlob, RWDBRow, RWDBValue, RWDlistCollectables, RWHashDictionary, RWHashTable, RWIdentityDictionary, RWIdentitySet, RWOrdered, RWSlistCollectablesQueue, RWBag, RWSet, RWSlistCollectables, RWSortedVector, RWSlistCollectablesStack, and RWCollectableDateTime.

static bool RWCollectable::isAtom

(

RWClassID

id

)

[static]

Returns true if id is the RWClassID that is associated with an RWCollectable class that has a programmer-chosen RWStringID.

virtual bool RWCollectable::isEqual

(

const RWCollectable *

t

)

const [virtual]

Returns true if the collectable object "matches" the object at address t. The default definition is:

 return this == t;

i.e., both objects have the same address (a test for identity). The definition may be redefined in any consistent way.

Reimplemented in RWBinaryTree, RWBTreeDictionary, RWBTree, RWCollectableAssociation, RWCollectableDate, RWCollectableInt, RWCollectableString, RWCollectableWString, RWCollectableTime, RWDBBlob, RWDBCollectableExpr, RWDBValue, RWDlistCollectables, RWHashDictionary, RWHashTable, RWIdentityDictionary, RWIdentitySet, RWOrdered, RWSlistCollectablesQueue, RWBag, RWSet, RWSlistCollectables, RWSortedVector, RWSlistCollectablesStack, and RWCollectableDateTime.

virtual RWCollectable* RWCollectable::newSpecies

(

)

const [virtual]

Allocates a new object off the heap of the same type as self and returns a pointer to it. You are responsible for deleting the object when done with it.

Reimplemented in RWBinaryTree, RWBTreeDictionary, RWBTree, RWCollectableAssociation, RWCollectableDate, RWCollectableInt, RWCollectableString, RWCollectableWString, RWCollectableTime, RWDBBlob, RWDBRow, RWDBValue, RWDlistCollectables, RWHashDictionary, RWHashTable, RWIdentityDictionary, RWIdentitySet, RWOrdered, RWSlistCollectablesQueue, RWBag, RWSet, RWSlistCollectables, RWSortedVector, RWSlistCollectablesStack, and RWCollectableDateTime.

static RWspace RWCollectable::nilStoreSize

(

)

[inline, static]

Returns the number of bytes required to store an rwnil pointer in an RWFile.

RWspace RWCollectable::recursiveStoreSize

(

)

const

Returns the number of bytes required to store the object using the global operator:

 RWFile& operator<<(RWFile&, const RWCollectable&);

Recursively calls binaryStoreSize(), taking duplicate objects into account.

virtual void RWCollectable::restoreGuts

(

RWvistream &

)

[virtual]

Reads an object's state from an input stream, replacing the previous state.

Reimplemented in RWCollection, RWCollectableAssociation, RWCollectableDate, RWCollectableInt, RWCollectableString, RWCollectableWString, RWCollectableTime, RWDBBlob, RWDBValue, RWSlistCollectablesStack, and RWCollectableDateTime.

virtual void RWCollectable::restoreGuts

(

RWFile &

)

[virtual]

Reads an object's state from a binary file, using class RWFile, replacing the previous state.

Reimplemented in RWCollection, RWCollectableAssociation, RWCollectableDate, RWCollectableInt, RWCollectableString, RWCollectableWString, RWCollectableTime, RWDBBlob, RWDBValue, RWSlistCollectablesStack, and RWCollectableDateTime.

virtual void RWCollectable::saveGuts

(

RWvostream &

)

const [virtual]

Writes an object's state to an output stream.

Reimplemented in RWBinaryTree, RWCollection, RWCollectableAssociation, RWCollectableDate, RWCollectableInt, RWCollectableString, RWCollectableWString, RWCollectableTime, RWDBBlob, RWDBValue, and RWCollectableDateTime.

virtual void RWCollectable::saveGuts

(

RWFile &

)

const [virtual]

Writes an object's state to a binary file, using class RWFile.

Reimplemented in RWBinaryTree, RWCollection, RWCollectableAssociation, RWCollectableDate, RWCollectableInt, RWCollectableString, RWCollectableWString, RWCollectableTime, RWDBBlob, RWDBValue, and RWCollectableDateTime.

RWStringID RWCollectable::stringID

(

)

const [inline]

Returns the identification string for the class. Acts virtual, although it is not. See the discussion on RWStringID in the Essential Tools Module User's Guide for more information on how to make a non-virtual function act like a virtual function.

---

Friends And Related Function Documentation

RWFile& operator<<	(	RWFile &	f,
		const RWCollectable &	obj
	)			[friend]

Saves the object obj to an RWFile. Recursively calls the virtual function saveGuts(), taking duplicate objects into account. See the discussion on Persistence in the Essential Tools Module User's Guide for more information.

RWvostream& operator<<	(	RWvostream &	v,
		const RWCollectable &	obj
	)			[friend]

Saves the object obj to a virtual stream. Recursively calls the virtual function saveGuts(), taking duplicate objects into account. See the discussion on Persistence in the Essential Tools Module User's Guide for more information.

RWFile& operator>>	(	RWFile &	f,
		RWCollectable &	obj
	)			[friend]

Restores an object inheriting from RWCollectable into obj from an RWFile, replacing the previous contents of obj. Recursively calls the virtual function restoreGuts(), taking duplicate objects into account. For more information, see the discussion on Persistence in the Essential Tools Module User's Guide.

Various exceptions that could be thrown are RWInternalErr (if the RWFactory does not know how to make the object), and RWExternalErr (corrupted stream or file).

RWvistream& operator>>	(	RWvistream &	v,
		RWCollectable &	obj
	)			[friend]

Restores an object inheriting from RWCollectable into obj from a virtual stream, replacing the previous contents of obj. Recursively calls the virtual function restoreGuts(), taking duplicate objects into account. For more information, see the discussion on Persistence in the Essential Tools Module User's Guide.

Various exceptions that could be thrown are RWInternalErr (if the RWFactory does not know how to make the object), and RWExternalErr (corrupted stream or file).

RWFile& operator>>	(	RWFile &	f,
		RWCollectable *&	pCl
	)			[friend]

Looks at the next object on the input stream or RWFile, respectively, and either creates a new object of the proper type off the heap and returns a pointer to it, or else returns a pointer to a previously read instance. Recursively calls the virtual function restoreGuts(), taking duplicate objects into account. If an object is created off the heap, then you are responsible for deleting it. For more information, see the discussion on Persistence in the Essential Tools Module User's Guide.

Various exceptions that could be thrown are RWInternalErr (if the RWFactory does not know how to make the object), and RWExternalErr (corrupted stream or file). If an exception is thrown during this call, the pointer to the partly restored object may be lost, creating a memory leak. For this reason, you may prefer to use the static methods tryRecursiveRestore().

RWvistream& operator>>	(	RWvistream &	s,
		RWCollectable *&	pCl
	)			[friend]

Looks at the next object on the input stream or RWFile, respectively, and either creates a new object of the proper type off the heap and returns a pointer to it, or else returns a pointer to a previously read instance. Recursively calls the virtual function restoreGuts(), taking duplicate objects into account. If an object is created off the heap, then you are responsible for deleting it. For more information, see the discussion on Persistence in the Essential Tools Module User's Guide.

Various exceptions that could be thrown are RWInternalErr (if the RWFactory does not know how to make the object), and RWExternalErr (corrupted stream or file). If an exception is thrown during this call, the pointer to the partly restored object may be lost, creating a memory leak. For this reason, you may prefer to use the static methods tryRecursiveRestore().