![[OPUS]](opus.gif)
This class is available for the OPUS Blackboard API. The initial OPUS 2.0 release is described here
Constructors:
| Field( ) | |
| ~Field( ) |
Methods:
| operator=( ) | field assignment operator |
| operator==( ) | tests for equality between fields |
| operator%( ) | applies differences between fields |
| clone( ) | creates a copy of this object |
| assign( ) | assigns a string to this object |
| fill( ) | fills the field with pad (or indicated) characters |
| upper( ) | upper-cases the field |
| lower( ) | lower-cases the field |
| id( ) | gets the field ID |
| str( ) | gets the string representation of the field (with padding) |
| ustr( ) | gets the string representation of the field (unpadded) |
| size( ) | gets the field width |
| name( ) | gets the field name |
Data Members:
enum PAD { UNDER = '_', DASH = '-', SPACE = ' ', // allowed pad
TAB = '\t'}; // characters
static const char FORCEPAD; // signals that
// padding should be
// used at a position
// during a % operation
Description
Blackboard entries are composed of any number of Field objects. Each field of an entry has a unique integer ID, a fixed size, and a default pad character. OPUS blackboard polling usually means searching for one or more entries based on equality or wildcarding of fields. Once a match is found to the polling condition, entries are marked as having triggered an event by applying a field "modifier" to a single field in each matching entry using operator%. This prevents other processes, or the same process, from retriggering on the same blackboard entries each time through the polling loop. Once an event is processed, the entries that triggered that event can be updated on the blackboard using another field modifier (often applied to the same field as when the event was triggered).
Derived from
See Also:
Field::Field - The Field constructor.
Synopsis
Field::Field(
const int id, // I - field ID
const int sz, // I - field width
const PAD pd) // I - default pad character
Field::Field(
const Field& f) // I - field to initialize from
Description
The constructor creates a new Field object with a unique ID, a field width, and pad character. By default, the underscore character is used for padding. The field is padded with the pad character after construction.
Exceptions Thrown
Example
Field* f = new Field(0, 5, Field::UNDER); // create new field with ID
// 0, width 5, and underscore
// padding
Field::~Field - The Field destructor.
Synopsis
Field::~Field()
Description
This method destroys the object.
Exceptions Thrown
Field::operator= - Field assignment operator.
Synopsis
Field& Field::operator=(
const Field& rhs) // I - the field to assign from
Description
Given a Field object with the same ID as this object, the field contents of the argument are assigned to this object.
Returns
A reference to this object.
Exceptions Thrown
| Type<Field*> | - if the field ID's do not match; Type.arg points to the calling argument |
Field::clone - Create a copy of this object.
Synopsis
Field* Field::clone() const
Description
A new Field object is constructed off the heap and initialized with the contents of this object. The client should delete the new object when it is no longer needed.
Returns
A pointer to a new Field object initialized with this object.
Exceptions Thrown
Field::operator== - Compare the Field object with another.
Synopsis
bool Field::operator==(
const Field* ff) // I - field to compare with
const
Description
This operator performs an equality comparison between the object and the argument. Two fields are equal if they have the same ID and if their unpadded string representations are identical. This method returns true if the fields are equal, and false if they do not satisfy the equality conditions.
***Note that a pointer to the object with which the comparison is to be made is required, not a reference.
Returns
true - if the object meets the equality conditions stated in the
description.
false - if the object and argument are not identical as stated in
the description.
Exceptions Thrown
Example
// compare two Field objects
Field* a = new Field(0, 10);
Field* b = new Field(0, 10);
if (*a == b) cout << "Fields are equal.";
Field::operator% - Apply field modifier to this object.
Synopsis
void Field::operator%(
Field* rhs) // I - modifier to compare with
Description
operator% does a character by character comparison between the object and the argument (the modifier) which must be a Field object of the same type and ID. Any character that differs between the two is replaced in the object with the argument's value. Padding is not considered significant unless a special FORCEPAD character is used in the modifier in which case the character in that position in the object is replaced with the pad character.
Returns
A pointer to this object.
Exceptions Thrown
| Bad_val<Field*> | - if the argument is null; Bad_val.arg points at the calling argument |
| Type<Field*> | - if the field types or ID's don't match; Type.arg points at the calling argument |
Example
Field* f = new Field(0, 8, UNDER);
Field* g = f->clone;
f->assign("ABCDEFGH");
g->assign("AB__XYZ!");
*f % g; // set *f to "ABCDXYZ_"
Field::assign - Assign a string to the object.
Synopsis
void Field::assign(
const string& s) // I - the string to assign
Description
This method sets the value of the field equal to the argument. If the string is longer than the field width, only width characters are assigned. If the string is shorter than the field width, the field is padded to width.
Exceptions Thrown
Field::fill - Fill field with pad or specified character.
Synopsis
void Field::fill(
const char c) // I - fill character or 0 for pad
Description
This method fills the field with the default pad character or the provided character out to the field width.
Exceptions Thrown
Field::upper - Change field to all upper case.
Synopsis
void Field::upper()
Description
Each character in the field is converted to uppercase.
Exceptions Thrown
Field::lower - Change field to all lower case
Synopsis
void Field::lower()
Description
Each character in the field is changed to lowercase.
Exceptions Thrown
Field::id - Get the field ID.
Synopsis
int Field::id() const
Description
This method returns the ID associated with this field.
Returns
The integer field ID.
Exceptions Thrown
Field::size - Get the field width.
Synopsis
int Field::size() const
Description
This method returns the width in characters of the field.
Returns
The integer field width.
Exceptions Thrown
Field::str - Get string representation of the object.
Synopsis
string Field::str() const
Description
This method returns the string value of the field, including pad characters.
Returns
string containing the value of the field with any padding
Exceptions Thrown
Field::ustr - Get string representation of the object (unpadded).
Synopsis
string Field::ustr() const
Description
This method returns the string value of the field string with any padding removed. If the field is nothing but padding, the empty string is returned.
Returns
a string containing the value of the field, less padding (an
empty string if the field is all padding)
Exceptions Thrown
Field::name - Get the name of the field.
Synopsis
string Field::name() const
Description
This method returns the field name, "FIELD".
Returns
the string "FIELD"
Exceptions Thrown
Copyright © 1997-2000 The Association of Universities for
Research in Astronomy, Inc. All Rights Reserved.
For more information, contact opushelp@stsci.edu
Last modified: 25 April 2000