Once the object referred to by a reference is deleted, use of the reference accesses arbitrary data and might cause a segmentation violation.
You can create a reference to serve as substitute for a pointer by initializing a variable of type os_reference_this_DB with the pointer, or by assigning the pointer to a variable of type os_reference_this_DB (implicitly invoking the conversion constructor os_reference_this_DB::os_reference_this_DB(void*)). In general, a pointer can be used anywhere an os_reference_this_DB is expected, and the conversion constructor will be invoked.
part *a_part = ... ;
os_reference_this_DB part_ref = a_part;
When an os_reference_this_DB is cast to pointer-to-referent-type (that is, pointer to the type of object referred to by the reference), os_reference_this_DB::operator void*() is implicitly invoked, returning a valid pointer to the object referred to by the os_reference_this_DB.
printf("%d\n", (part*)(part_ref)->part_id);
Performing the member function resolve() on an os_reference_this_DB returns a valid pointer to the object referred to by the os_reference_this_DB.
printf("%d\n", part_ref.>resolve()->part_id);
The types os_int32 and os_boolean, used throughout this manual, are each defined as a signed 32-bit integer type. The type os_unsigned_int32 is defined as an unsigned 32-bit integer type.
All ObjectStore programs must include the header file <ostore\ostore.hh>.
char* dump(const char* db_str) const;Returns a heap-allocated string for the reference that the method was called. However, unlike the string returned by the char* os_reference_this_DB::dump(void) method, the returned string does not contain an absolute database pathname. The returned string is intended for use as the dump_str parameter of an os_reference_this_DB load method of the form load(const char* dump_str, os_database* db). It is the responsibility of the caller of load to ensure that the db parameter passed to the load method is the same as the database of the dumped reference. It is the user's responsibility to delete the returned string when finished using the string.
This operation is useful in those applications in which you do not want the overhead of storing the absolute database path in the dumped strings.
os_database *get_database() const;Returns a pointer to the database containing the object referred to by the specified reference.
char* get_database_key(const char* dump_str);Returns a heap-allocated string containing the database_key component of the string dump_str. dump_str must have been generated using the dump operation. Otherwise, the exception err_reference_syntax is raised. It is the user's responsibility to delete the returned string when finished using the string.
static os_typespec *get_os_typespec();Returns an os_typespec* for the class os_reference_this_DB.
os_unsigned_int32 hash() const;Returns an integer suitable for use as a hash table key. The value returned is always the same for a reference to a given referent.
void load(const char* dump_str, const os_database* db);The dump_str parameter is assumed to be the result of a call to a compatible os_reference dump method. It is the responsibility of the caller of load to ensure that the db parameter passed to the load method is the same as the database of the originally dumped reference. The loaded reference refers to the same object as the os_reference used to dump the string as long as the db parameter is the same as the database of the dumped reference. The exception err_reference_syntax is raised if the dump_str is not in the expected format.
operator void*() const;Returns the valid pointer for which the specified reference is a substitute.
os_reference_this_DB &operator=(Establishes the referent of the right operand as the referent of the left operand.
const os_reference_this_DB&
);
os_reference_this_DB &operator=(const void*);Establishes the object pointed to by the right operand as the referent of the left operand.
os_boolean operator ==(os_reference_this_DB const&) const;Returns 1 if the arguments have the same referent; returns 0 otherwise.
os_boolean operator !=(os_reference_this_DB const&) const;Returns 1 if the arguments have different referents; returns 0 otherwise.
os_boolean operator <(os_reference_this_DB const&) const;If the first argument and second argument refer to elements of the same array or one beyond the end of the array, a return value of 1 indicates that the referent of the first argument precedes the referent of the second, and a return value of 0 indicates that it does not. Otherwise the results are undefined.
os_boolean operator >(os_reference_this_DB const&) const;If the first argument and second argument refer to elements of the same array or one beyond the end of the array, a return value of 1 indicates that the referent of the first argument follows the referent of the second, and a return value of 0 indicates that it does not. Otherwise the results are undefined.
os_boolean operator >=(os_reference_this_DB const&) const;If the first argument and second argument refer to elements of the same array or one beyond the end of the array, a return value of 1 indicates that the referent of the first argument follows or is the same as the referent of the second, and a return value of 0 indicates that it does not. Otherwise the results are undefined.
os_boolean operator <=(os_reference_this_DB const&) const;If the first argument and second argument refer to elements of the same array or one beyond the end of the array, a return value of 1 indicates that the referent of the first argument precedes or is the same as the referent of the second, and a return value of 0 indicates that it does not. Otherwise the results are undefined.
os_reference_this_DB(const void*);Constructs a reference to substitute for the specified void*.
void* resolve() const;Returns the valid void* for which the specified reference is a substitute.
Updated: 03/31/98 17:25:09