QSqlField(3qt) QSqlField(3qt)
NAME
QSqlField - Manipulates the fields in SQL database tables and views
SYNOPSIS
#include <qsqlfield.h>
Public Members
QSqlField ( const QString & fieldName = QString::null, QVariant::Type type = QVariant::Invalid )
QSqlField ( const QSqlField & other )
QSqlField & operator= ( const QSqlField & other )
bool operator== ( const QSqlField & other ) const
virtual ~QSqlField ()
virtual void setValue ( const QVariant & value )
virtual QVariant value () const
virtual void setName ( const QString & name )
QString name () const
virtual void setNull ()
bool isNull () const
virtual void setReadOnly ( bool readOnly )
bool isReadOnly () const
void clear ( bool nullify = TRUE )
QVariant::Type type () const
DESCRIPTION
The QSqlField class manipulates the fields in SQL database tables and views.
QSqlField represents the characteristics of a single column in a database table or view, such as the data type and column name. A field
also contains the value of the database column, which can be viewed or changed.
Field data values are stored as QVariants. Using an incompatible type is not permitted. For example:
QSqlField f( "myfield", QVariant::Int );
f.setValue( QPixmap() ); // will not work
However, the field will attempt to cast certain data types to the field data type where possible:
QSqlField f( "myfield", QVariant::Int );
f.setValue( QString("123") ); // casts QString to int
QSqlField objects are rarely created explicitly in application code. They are usually accessed indirectly through QSqlRecord or QSqlCursor
which already contain a list of fields. For example:
QSqlCursor cur( "Employee" ); // create cursor using the 'Employee' table
QSqlField* f = cur.field( "name" ); // use the 'name' field
f->setValue( "Dave" ); // set field value
...
In practice we rarely need to extract a pointer to a field at all. The previous example would normally be written:
QSqlCursor cur( "Employee" );
cur.setValue( "name", "Dave" );
...
See also Database Classes.
MEMBER FUNCTION DOCUMENTATION
QSqlField::QSqlField ( const QString & fieldName = QString::null, QVariant::Type type = QVariant::Invalid )
Constructs an empty field called fieldName of type type.
QSqlField::QSqlField ( const QSqlField & other )
Constructs a copy of other.
QSqlField::~QSqlField () [virtual]
Destroys the object and frees any allocated resources.
void QSqlField::clear ( bool nullify = TRUE )
Clears the value of the field. If the field is read-only, nothing happens. If nullify is TRUE (the default), the field is set to NULL.
bool QSqlField::isNull () const
Returns TRUE if the field is currently NULL; otherwise returns FALSE.
bool QSqlField::isReadOnly () const
Returns TRUE if the field's value is read only; otherwise returns FALSE.
QString QSqlField::name () const
Returns the name of the field.
Example: sql/overview/table4/main.cpp.
QSqlField &; QSqlField::operator= ( const QSqlField & other )
Sets the field equal to other.
bool QSqlField::operator== ( const QSqlField & other ) const
Returns TRUE if the field is equal to other; otherwise returns FALSE. Fields are considered equal when the following field properties are
the same:
name()
isNull()
value()
isReadOnly()
void QSqlField::setName ( const QString & name ) [virtual]
Sets the name of the field to name.
void QSqlField::setNull () [virtual]
Sets the field to NULL and clears the value using clear(). If the field is read-only, nothing happens.
See also isReadOnly() and clear().
void QSqlField::setReadOnly ( bool readOnly ) [virtual]
Sets the read only flag of the field's value to readOnly.
See also setValue().
void QSqlField::setValue ( const QVariant & value ) [virtual]
Sets the value of the field to value. If the field is read-only (isReadOnly() returns TRUE), nothing happens. If the data type of value
differs from the field's current data type, an attempt is made to cast it to the proper type. This preserves the data type of the field in
the case of assignment, e.g. a QString to an integer data type. For example:
QSqlCursor cur( "Employee" ); // 'Employee' table
QSqlField* f = cur.field( "student_count" ); // an integer field
...
f->setValue( myLineEdit->text() ); // cast the line edit text to an integer
See also isReadOnly().
QVariant::Type QSqlField::type () const
Returns the field's type as stored in the database. Note that the actual value might have a different type, Numerical values that are too
large to store in a long int or double are usually stored as strings to prevent precision loss.
QVariant QSqlField::value () const [virtual]
Returns the value of the field as a QVariant.
Example: sql/overview/table4/main.cpp.
SEE ALSO
http://doc.trolltech.com/qsqlfield.html http://www.trolltech.com/faq/tech.html
COPYRIGHT
Copyright 1992-2007 Trolltech ASA, http://www.trolltech.com. See the license file included in the distribution for a complete license
statement.
AUTHOR
Generated automatically from the source code.
BUGS
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Thank you.
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If you find errors in this manual page, please report them to qt-bugs@trolltech.com. Please include the name of the manual page
(qsqlfield.3qt) and the Qt version (3.3.8).
Trolltech AS 2 February 2007 QSqlField(3qt)