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qsqlfield.cpp

/****************************************************************************
**
** Copyright (C) 1992-2007 Trolltech ASA. All rights reserved.
**
** This file is part of the QtSql module of the Qt Toolkit.
**
** This file may be used under the terms of the GNU General Public
** License version 2.0 as published by the Free Software Foundation
** and appearing in the file LICENSE.GPL included in the packaging of
** this file.  Please review the following information to ensure GNU
** General Public Licensing requirements will be met:
** http://www.trolltech.com/products/qt/opensource.html
**
** If you are unsure which license is appropriate for your use, please
** review the following information:
** http://www.trolltech.com/products/qt/licensing.html or contact the
** sales department at sales@trolltech.com.
**
** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
**
****************************************************************************/

#include "qsqlfield.h"
#include "qatomic.h"
#include "qdebug.h"

class QSqlFieldPrivate
{
public:
    QSqlFieldPrivate(const QString &name,
              QVariant::Type type) :
        ref(1), nm(name), ro(false), type(type), req(QSqlField::Unknown),
        len(-1), prec(-1), tp(-1), gen(true), autoval(false)
    {
    }

    QSqlFieldPrivate(const QSqlFieldPrivate &other)
        : ref(1),
          nm(other.nm),
          ro(other.ro),
          type(other.type),
          req(other.req),
          len(other.len),
          prec(other.prec),
          def(other.def),
          tp(other.tp),
          gen(other.gen),
          autoval(other.autoval)
    {}

    bool operator==(const QSqlFieldPrivate& other) const
    {
        return (nm == other.nm
                && ro == other.ro
                && type == other.type
                && req == other.req
                && len == other.len
                && prec == other.prec
                && def == other.def
                && tp == other.tp
                && gen == other.gen
                && autoval == other.autoval);
    }

    QAtomic ref;
    QString nm;
    uint ro: 1;
    QVariant::Type type;
    QSqlField::RequiredStatus req;
    int len;
    int prec;
    QVariant def;
    int tp;
    uint gen: 1;
    uint autoval: 1;
};


/*!
    \class QSqlField
    \brief The QSqlField class manipulates the fields in SQL database tables
    and views.

    \ingroup database
    \ingroup shared
    \module sql

    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:

    \quotefromfile snippets/sqldatabase/sqldatabase.cpp
    \skipto QSqlField_snippets
    \skipto QSqlField field
    \printuntil setValue

    However, the field will attempt to cast certain data types to the
    field data type where possible:

    \skipto QSqlField field
    \printuntil setValue

    QSqlField objects are rarely created explicitly in application
    code. They are usually accessed indirectly through \l{QSqlRecord}s
    that already contain a list of fields. For example:

    \skipto QSqlQuery query
    \printline QSqlQuery query
    \dots
    \printline QSqlRecord record
    \printline QSqlField field

    A QSqlField object can provide some meta-data about the field, for
    example, its name(), variant type(), length(), precision(),
    defaultValue(), typeID(), and its requiredStatus(),
    isGenerated() and isReadOnly(). The field's data can be
    checked to see if it isNull(), and its value() retrieved. When
    editing the data can be set with setValue() or set to NULL with
    clear().

    \sa QSqlRecord
*/

/*!
    \enum QSqlField::RequiredStatus

    Specifies whether the field is required or optional.

    \value Required  The field must be specified when inserting records.
    \value Optional  The fields doesn't have to be specified when inserting records.
    \value Unknown  The database driver couldn't determine whether the field is required or
                    optional.

    \sa requiredStatus()
*/

/*!
    Constructs an empty field called \a fieldName of variant type \a
    type.

    \sa setRequiredStatus() setLength() setPrecision() setDefaultValue() setGenerated() setReadOnly()
*/
00148 QSqlField::QSqlField(const QString& fieldName, QVariant::Type type)
{
    d = new QSqlFieldPrivate(fieldName, type);
}

/*!
    Constructs a copy of \a other.
*/

00157 QSqlField::QSqlField(const QSqlField& other)
{
    d = other.d;
    d->ref.ref();
    val = other.val;
}

/*!
    Sets the field equal to \a other.
*/

00168 QSqlField& QSqlField::operator=(const QSqlField& other)
{
    qAtomicAssign(d, other.d);
    val = other.val;
    return *this;
}


/*! \fn bool QSqlField::operator!=(const QSqlField &other) const
    Returns true if the field is unequal to \a other; otherwise returns
    false.
*/

/*!
    Returns true if the field is equal to \a other; otherwise returns
    false.
*/
00185 bool QSqlField::operator==(const QSqlField& other) const
{
    return ((d == other.d || *d == *other.d)
            && val == other.val);
}

/*!
    Destroys the object and frees any allocated resources.
*/

00195 QSqlField::~QSqlField()
{
    if (!d->ref.deref())
        delete d;
}

/*!
    Sets the required status of this field to \a required.

    \sa requiredStatus() setType() setLength() setPrecision() setDefaultValue() setGenerated() setReadOnly()
*/
00206 void QSqlField::setRequiredStatus(RequiredStatus required)
{
    detach();
    d->req = required;
}

/*! \fn void QSqlField::setRequired(bool required)

    Sets the required status of this field to \l Required if \a
    required is true; otherwise sets it to \l Optional.

    \sa setRequiredStatus(), requiredStatus()
*/

/*!
    Sets the field's length to \a fieldLength. For strings this is the
    maximum number of characters the string can hold; the meaning
    varies for other types.

    \sa length() setType() setRequiredStatus() setPrecision() setDefaultValue() setGenerated() setReadOnly()
*/
00227 void QSqlField::setLength(int fieldLength)
{
    detach();
    d->len = fieldLength;
}

/*!
    Sets the field's \a precision. This only affects numeric fields.

    \sa precision() setType() setRequiredStatus() setLength() setDefaultValue() setGenerated() setReadOnly()
*/
00238 void QSqlField::setPrecision(int precision)
{
    detach();
    d->prec = precision;
}

/*!
    Sets the default value used for this field to \a value.

    \sa defaultValue() value() setType() setRequiredStatus() setLength() setPrecision() setGenerated() setReadOnly()
*/
00249 void QSqlField::setDefaultValue(const QVariant &value)
{
    detach();
    d->def = value;
}

/*!
    \internal
*/
00258 void QSqlField::setSqlType(int type)
{
    detach();
    d->tp = type;
}

/*!
    Sets the generated state. If \a gen is false, no SQL will
    be generated for this field; otherwise, Qt classes such as
    QSqlQueryModel and QSqlTableModel will generate SQL for this
    field.

    \sa isGenerated() setType() setRequiredStatus() setLength() setPrecision() setDefaultValue() setReadOnly()
*/
00272 void QSqlField::setGenerated(bool gen)
{
    detach();
    d->gen = gen;
}


/*!
    Sets the value of the field to \a value. If the field is read-only
    (isReadOnly() returns true), nothing happens.

    If the data type of \a 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.

    To set the value to NULL, use clear().

    \sa value() isReadOnly() defaultValue()
*/

00293 void QSqlField::setValue(const QVariant& value)
{
    if (isReadOnly())
        return;
    val = value;
}

/*!
    Clears the value of the field and sets it to NULL.
    If the field is read-only, nothing happens.

    \sa setValue() isReadOnly() requiredStatus()
*/

00307 void QSqlField::clear()
{
    if (isReadOnly())
        return;
    val = QVariant(type());
}

/*!
    Sets the name of the field to \a name.

    \sa name()
*/

00320 void QSqlField::setName(const QString& name)
{
    detach();
    d->nm = name;
}

/*!
    Sets the read only flag of the field's value to \a readOnly. A
    read-only field cannot have its value set with setValue() and
    cannot be cleared to NULL with clear().
*/
00331 void QSqlField::setReadOnly(bool readOnly)
{
    detach();
    d->ro = readOnly;
}

/*!
    \fn QVariant QSqlField::value() const

    Returns the value of the field as a QVariant.

    Use isNull() to check if the field's value is NULL.
*/

/*!
    Returns the name of the field.

    \sa setName()
*/
00350 QString QSqlField::name() const
{
    return d->nm;
}

/*!
    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.

    \sa setType()
*/
00364 QVariant::Type QSqlField::type() const
{
    return d->type;
}

/*!
    Set's the field's variant type to \a type.

    \sa type() setRequiredStatus() setLength() setPrecision() setDefaultValue() setGenerated() setReadOnly()
*/
00374 void QSqlField::setType(QVariant::Type type)
{
    detach();
    d->type = type;
}


/*!
    Returns true if the field's value is read-only; otherwise returns
    false.

    \sa setReadOnly() type() requiredStatus() length() precision() defaultValue() isGenerated()
*/
00387 bool QSqlField::isReadOnly() const
{ return d->ro; }

/*!
    Returns true if the field's value is NULL; otherwise returns
    false.

    \sa value()
*/
00396 bool QSqlField::isNull() const
{ return val.isNull(); }

/*! \internal
*/
00401 void QSqlField::detach()
{
    qAtomicDetach(d);
}

/*!
    Returns true if this is a required field; otherwise returns false.
    An \c INSERT will fail if a required field does not have a value.

    \sa setRequiredStatus() type() length() precision() defaultValue() isGenerated()
*/
00412 QSqlField::RequiredStatus QSqlField::requiredStatus() const
{
    return d->req;
}

/*!
    Returns the field's length.

    If the returned value is negative, it means that the information
    is not available from the database.

    \sa setLength() type() requiredStatus() precision() defaultValue() isGenerated()
*/
00425 int QSqlField::length() const
{
    return d->len;
}

/*!
    Returns the field's precision; this is only meaningful for numeric
    types.

    If the returned value is negative, it means that the information
    is not available from the database.

    \sa setPrecision() type() requiredStatus() length() defaultValue() isGenerated()
*/
00439 int QSqlField::precision() const
{
    return d->prec;
}

/*!
    Returns the field's default value (which may be NULL).

    \sa setDefaultValue() type() requiredStatus() length() precision() isGenerated()
*/
00449 QVariant QSqlField::defaultValue() const
{
    return d->def;
}

/*!
    \internal

    Returns the type ID for the field.

    If the returned value is negative, it means that the information
    is not available from the database.
*/
00462 int QSqlField::typeID() const
{
    return d->tp;
}

/*!
    Returns true if the field is generated; otherwise returns
    false.

    \sa setGenerated() type() requiredStatus() length() precision() defaultValue()
*/
00473 bool QSqlField::isGenerated() const
{
    return d->gen;
}

/*!
    Returns true if the field's variant type is valid; otherwise
    returns false.
*/
00482 bool QSqlField::isValid() const
{
    return d->type != QVariant::Invalid;
}

#ifndef QT_NO_DEBUG_STREAM
QDebug operator<<(QDebug dbg, const QSqlField &f)
{
#ifndef Q_BROKEN_DEBUG_STREAM
    dbg.nospace() << "QSqlField(" << f.name() << ", " << QVariant::typeToName(f.type());
    if (f.length() >= 0)
        dbg.nospace() << ", length: " << f.length();
    if (f.precision() >= 0)
        dbg.nospace() << ", precision: " << f.precision();
    if (f.requiredStatus() != QSqlField::Unknown)
        dbg.nospace() << ", required: "
                      << (f.requiredStatus() == QSqlField::Required ? "yes" : "no");
    dbg.nospace() << ", generated: " << (f.isGenerated() ? "yes" : "no");
    if (f.typeID() >= 0)
        dbg.nospace() << ", typeID: " << f.typeID();
    if (!f.defaultValue().isNull())
        dbg.nospace() << ", auto-value: \"" << f.defaultValue() << "\"";
    dbg.nospace() << ")";
    return dbg.space();
#else
    qWarning("This compiler doesn't support streaming QSqlField to QDebug");
    return dbg;
    Q_UNUSED(f);
#endif
}
#endif

/*!
    \fn void QSqlField::setNull()

    Use clear() instead.
*/

/*!
    Returns true if the value is auto-generated by the database,
    for example auto-increment primary key values.

    \sa setAutoValue()
*/
00526 bool QSqlField::isAutoValue() const
{
    return d->autoval;
}

/*!
    Marks the field as an auto-generated value if \a autoVal
    is true.

    \sa isAutoValue()
 */
00537 void QSqlField::setAutoValue(bool autoVal)
{
    detach();
    d->autoval = autoVal;
}


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