Ref Class

The mapping in the C++ programming language of an SQL REF value, which is a reference to an SQL structured type value in the database.

Each REF value has a unique identifier of the object it refers to. An SQL REF value may be used istead of the SQL structured type it references; it may be used as either a column value in a table or an attribute value in a structured type.

Because an SQL REF value is a logical pointer to an SQL structured type, a Ref object is by default also a logical pointer; thus, retrieving an SQL REF value as a Ref object does not materialize the attributes of the structured type on the client.

The only methods valid on a NULL Ref object are isNull(), and operator=().

A Ref object can be saved to persistent storage and is de-referenced through operator*(), operator->() or ptr() methods. T must be a class derived from PObject. In the following sections, T* and PObject* are used interchangeably.

LockOptions

PrefetchOption

Ref()

Ref object constructor.

Ref();

Ref(
   const Ref<T> &src);

src

clear()

This method clears the Ref object.

Syntax

void clear();

getConnection()

Returns the connection from which the Ref object was instantiated.

Syntax

const Connection *getConnection() const;

isClear()

This method checks if Ref object is cleared.

Syntax

bool isClear() const;

isNull()

This method tests whether the Ref object is NULL. If the Ref object is NULL, then TRUE is returned; otherwise, FALSE is returned.

Syntax

bool isNull() const;

markDelete()

This method marks the referenced object as deleted.

Syntax

void markDelete();

operator->()

This method dereferences the Ref object and pins, or fetches the referenced object if necessary. This might result in prefetching a graph of objects if prefetch attributes of the referenced object are set.

T *operator->();

const T *operator->() const;

operator*()

This method dereferences the Ref object and pins or fetches the referenced object if necessary. This might result in prefetching a graph of objects if prefetch attributes of the referenced object are set. The object does not have to be deleted. Destructor would be automatically called when it goes out of scope.

T& operator*();

const T& operator*() const;

operator==()

This method tests whether two Ref objects are referencing the same object. If the Ref objects are referencing the same object, then TRUE is returned; otherwise, FALSE is returned.

Syntax

bool operator == (
   const Ref<T> &ref) const;

ref

operator!=()

This method tests whether two Ref objects are referencing the same object. If the Ref objects are not referencing the same object, then TRUE is returned; otherwise, FALSE is returned.

Syntax

bool operator!= (
   const Ref<T> &ref) const;

ref

operator=()

Assigns the Ref or the object to a Ref. For the first case, the Refs are assigned and for the second case, the Ref is constructed from the object and then assigned.

Ref<T>& operator=(
   const Ref<T> &src);

Ref<T>& operator=(
   const T *)obj;

src

obj

ptr()

Returns a pointer to a PObject. This operator dereferences the Ref and pins or fetches the object if necessary. This might result in prefetching a graph of objects if prefetch attributes of the Ref are set.

T *ptr();

const T *ptr() const;

setLock()

This method specifies how the object should be locked when dereferenced.

Syntax

void setLock(lockOptions);

lockOptions

setNull()

This method sets the Ref object to NULL.

Syntax

void setNull();

setPrefetch()

Sets the prefetching options for complex object retrieval. This method specifies depth up to which all objects reachable from this object through Refs (transitive closure) should be prefetched. If only selected attribute types are to be prefetched, then the first version of the method must be used. This method specifies which Ref attributes of the object it refers to should be followed for prefetching of the objects (complex object retrieval) and how many levels deep those links should be followed.

void setPrefetch(
   const string &typeName,
   unsigned int depth);

void setPrefetch(
   unsigned int depth);

void setPrefetch(
   const string &schName,
   const string &typeName,
   unsigned int depth);

void setPrefetch(
   const UString &schName,
   const UString &typeName,
   unsigned int depth);

typeName

schName

depth

unmarkDelete()

This method unmarks the referred object as dirty and available for deletion.

Syntax

void unmarkDelete();