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QDBusArgument 类

QDBusArgument class is used to marshall and demarshall D-Bus arguments. 更多...

头： #include <QDBusArgument>
qmake: QT += dbus
Since: Qt 4.2

公共类型

enum ElementType { BasicType, VariantType, ArrayType, StructureType, ..., UnknownType }

公共函数

QDBusArgument ()
QDBusArgument (const QDBusArgument & other )
QDBusArgument (QDBusArgument && other )
~QDBusArgument ()
QVariant asVariant () const
bool atEnd () const
void beginArray (int id )
void beginArray () const
void beginMap (int kid , int vid )
void beginMap () const
void beginMapEntry ()
void beginMapEntry () const
void beginStructure ()
void beginStructure () const
ElementType currentType () const
void endArray ()
void endArray () const
void endMap ()
void endMap () const
void endMapEntry ()
void endMapEntry () const
void endStructure ()
void endStructure () const
void swap (QDBusArgument & other )
QDBusArgument & operator<< (uchar arg )
QDBusArgument & operator<< (bool arg )
QDBusArgument & operator<< (short arg )
QDBusArgument & operator<< (ushort arg )
QDBusArgument & operator<< (int arg )
QDBusArgument & operator<< (uint arg )
QDBusArgument & operator<< (qlonglong arg )
QDBusArgument & operator<< (qulonglong arg )
QDBusArgument & operator<< (double arg )
QDBusArgument & operator<< (const QString & arg )
QDBusArgument & operator<< (const QDBusVariant & arg )
QDBusArgument & operator<< (const QStringList & arg )
QDBusArgument & operator<< (const QByteArray & arg )
QDBusArgument & operator= (QDBusArgument && other )
QDBusArgument & operator= (const QDBusArgument & other )
const QDBusArgument & operator>> (uchar & arg ) const
const QDBusArgument & operator>> (bool & arg ) const
const QDBusArgument & operator>> (short & arg ) const
const QDBusArgument & operator>> (ushort & arg ) const
const QDBusArgument & operator>> (int & arg ) const
const QDBusArgument & operator>> (uint & arg ) const
const QDBusArgument & operator>> (qlonglong & arg ) const
const QDBusArgument & operator>> (qulonglong & arg ) const
const QDBusArgument & operator>> (double & arg ) const
const QDBusArgument & operator>> (QString & arg ) const
const QDBusArgument & operator>> (QDBusVariant & arg ) const
const QDBusArgument & operator>> (QStringList & arg ) const
const QDBusArgument & operator>> (QByteArray & arg ) const
int qDBusRegisterMetaType ()
T qdbus_cast (const QDBusArgument & argument )

详细描述

QDBusArgument class is used to marshall and demarshall D-Bus arguments.

The class is used to send arguments over D-Bus to remote applications and to receive them back. D-Bus offers an extensible type system, based on a few primitive types and associations of them. See the Qt D-Bus Type System page for more information on the type system.

QDBusArgument is the central class in the Qt D-Bus type system, providing functions to marshall and demarshall the primitive types. The compound types are then created by association of one or more of the primitive types in arrays, dictionaries or structures.

The following example illustrates how a structure containing an integer and a string can be constructed using the Qt D-Bus type system : 

struct MyStructure
{
    int count;
    QString name;
};
Q_DECLARE_METATYPE(MyStructure)
// Marshall the MyStructure data into a D-Bus argument
QDBusArgument &operator<<(QDBusArgument &argument, const MyStructure &mystruct)
{
    argument.beginStructure();
    argument << mystruct.count << mystruct.name;
    argument.endStructure();
    return argument;
}
// Retrieve the MyStructure data from the D-Bus argument
const QDBusArgument &operator>>(const QDBusArgument &argument, MyStructure &mystruct)
{
    argument.beginStructure();
    argument >> mystruct.count >> mystruct.name;
    argument.endStructure();
    return argument;
}

The type has to be registered with qDBusRegisterMetaType () before it can be used with QDBusArgument . Therefore, somewhere in your program, you should add the following code: 

qDBusRegisterMetaType<MyStructure>();

Once registered, a type can be used in outgoing method calls (placed with QDBusAbstractInterface::call ()), signal emissions from registered objects or in incoming calls from remote applications.

It is important to note that the operator<< and operator>> streaming functions must always produce the same number of entries in case of structures, both in reading and in writing (marshalling and demarshalling), otherwise calls and signals may start to silently fail.

The following example illustrates this wrong usage in context of a class that may contain invalid data: 

//bad code
    // Wrongly marshall the MyTime data into a D-Bus argument
    QDBusArgument &operator<<(QDBusArgument &argument, const MyTime &mytime)
    {
        argument.beginStructure();
        if (mytime.isValid)
            argument << true << mytime.hour
                     << mytime.minute << mytime.second;
        else
            argument << false;
        argument.endStructure();
        return argument;
    }

In this example, both the operator<< 和 operator>> functions may produce a different number of reads/writes. This can confuse the Qt D-Bus type system and should be avoided.

另请参阅 QDBusAbstractInterface , The Qt D-Bus type system , Using Adaptors ，和 qdbus_cast ().

成员类型文档编制

enum QDBusArgument:: ElementType

This enum describes the type of element held by the argument.

常量 值 描述
QDBusArgument::BasicType 0 A basic element, which is understood by QVariant . The following types are considered basic: bool, byte, short, ushort, int, uint, qint64, quint64, double, QString , QByteArray , QDBusObjectPath , QDBusSignature
QDBusArgument::VariantType 1 The variant element ( QDBusVariant )
QDBusArgument::ArrayType 2 An array element, usually represented by QList <T> or QVector <T>. Note: QByteArray and associative maps are not considered arrays, even if the D-Bus protocol transports them as such.
QDBusArgument::StructureType 3 A custom type represented by a structure, like QDateTime , QPoint ，等。
QDBusArgument::MapType 4 An associative container, like QMap <Key, Value> or QHash <Key, Value>
QDBusArgument::MapEntryType 5 One entry in an associative container: both the key and the value form one map-entry type.
QDBusArgument::UnknownType -1 The type is unknown or we have reached the end of the list.

该枚举在 Qt 4.5 引入或被修改。

另请参阅 currentType ().

成员函数文档编制

QDBusArgument:: QDBusArgument ()

构造空的 QDBusArgument 自变量。

An empty QDBusArgument object does not allow either reading or writing to be performed.

QDBusArgument:: QDBusArgument (const QDBusArgument & other )

构造副本为 other QDBusArgument 对象。

Both objects will therefore contain the same state from this point forward. QDBusArguments are explicitly shared and, therefore, any modification to either copy will affect the other one too.

QDBusArgument:: QDBusArgument ( QDBusArgument && other )

移动拷贝构造函数。

QDBusArgument:: ~QDBusArgument ()

Disposes of the resources associated with this QDBusArgument 对象。

QVariant QDBusArgument:: asVariant () const

Returns the current argument in the form of a QVariant . Basic types will be decoded and returned in the QVariant , but for complex types, this function will return a QDBusArgument object in the QVariant . It is the caller's responsibility to decode the argument (for example, by calling asVariant() in it).

For example, if the current argument is an INT32, this function will return a QVariant with an argument of type QVariant::Int. For an array of INT32, it will return a QVariant 包含 QDBusArgument .

If an error occurs or if there are no more arguments to decode (i.e., we are at the end of the argument list), this function will return an invalid QVariant .

该函数在 Qt 4.5 引入。

另请参阅 atEnd ().

bool QDBusArgument:: atEnd () const

返回 true if there are no more elements to be extracted from this QDBusArgument . This function is usually used in QDBusArgument objects returned from beginMap () 和 beginArray ().

void QDBusArgument:: beginArray ( int id )

Opens a new D-Bus array suitable for appending elements of meta-type id .

This function is used usually in operator<< streaming operators, as in the following example: 

// append an array of MyElement types
QDBusArgument &operator<<(QDBusArgument &argument, const MyArray &myarray)
{
    argument.beginArray( qMetaTypeId<MyElement>() );
    for ( int i = 0; i < myarray.length; ++i )
        argument << myarray.elements[i];
    argument.endArray();
    return argument;
}

If the type you want to marshall is a QList , QVector or any of the Qt's 容器类 that take one template parameter, you need not declare an operator<< function for it, since Qt D-Bus provides generic templates to do the job of marshalling the data. The same applies for STL's sequence containers, such as std::list , std::vector ，等。

另请参阅 endArray (), beginStructure ()，和 beginMap ().

void QDBusArgument:: beginArray () const

Recurses into the D-Bus array to allow extraction of the array elements.

This function is used usually in operator>> streaming operators, as in the following example: 

// extract a MyArray array of MyElement elements
const QDBusArgument &operator>>(const QDBusArgument &argument, MyArray &myarray)
{
    argument.beginArray();
    myarray.clear();
    while ( !argument.atEnd() ) {
        MyElement element;
        argument >> element;
        myarray.append( element );
    }
    argument.endArray();
    return argument;
}

If the type you want to demarshall is a QList , QVector or any of the Qt's 容器类 that take one template parameter, you need not declare an operator>> function for it, since Qt D-Bus provides generic templates to do the job of demarshalling the data. The same applies for STL's sequence containers, such as std::list , std::vector ，等。

另请参阅 atEnd (), beginStructure ()，和 beginMap ().

void QDBusArgument:: beginMap ( int kid , int vid )

Opens a new D-Bus map suitable for appending elements. Maps are containers that associate one entry (the key) to another (the value), such as Qt's QMap or QHash . The ids of the map's key and value meta types must be passed in kid and vid 分别。

This function is used usually in operator<< streaming operators, as in the following example: 

// append a dictionary that associates ints to MyValue types
QDBusArgument &operator<<(QDBusArgument &argument, const MyDictionary &mydict)
{
    argument.beginMap( QVariant::Int, qMetaTypeId<MyValue>() );
    for ( int i = 0; i < mydict.length; ++i ) {
        argument.beginMapEntry();
        argument << mydict.data[i].key << mydict.data[i].value;
        argument.endMapEntry();
    }
    argument.endMap();
    return argument;
}

If the type you want to marshall is a QMap or QHash , you need not declare an operator<< function for it, since Qt D-Bus provides generic templates to do the job of marshalling the data.

另请参阅 endMap (), beginStructure (), beginArray ()，和 beginMapEntry ().

void QDBusArgument:: beginMap () const

Recurses into the D-Bus map to allow extraction of the map's elements.

This function is used usually in operator>> streaming operators, as in the following example: 

// extract a MyDictionary map that associates ints to MyValue elements
const QDBusArgument &operator>>(const QDBusArgument &argument, MyDictionary &mydict)
{
    argument.beginMap();
    mydict.clear();
    while ( !argMap.atEnd() ) {
        int key;
        MyValue value;
        argument.beginMapEntry();
        argument >> key >> value;
        argument.endMapEntry();
        mydict.append( key, value );
    }
    argument.endMap();
    return argument;
}

If the type you want to demarshall is a QMap or QHash , you need not declare an operator>> function for it, since Qt D-Bus provides generic templates to do the job of demarshalling the data.

另请参阅 endMap (), beginStructure (), beginArray ()，和 beginMapEntry ().

void QDBusArgument:: beginMapEntry ()

Opens a D-Bus map entry suitable for appending the key and value entries. This function is only valid when a map has been opened with beginMap ().

见 beginMap () for an example of usage of this function.

另请参阅 endMapEntry () 和 beginMap ().

void QDBusArgument:: beginMapEntry () const

Recurses into the D-Bus map entry to allow extraction of the key and value pair.

见 beginMap () for an example of how this function is usually used.

另请参阅 endMapEntry () 和 beginMap ().

void QDBusArgument:: beginStructure ()

Opens a new D-Bus structure suitable for appending new arguments.

This function is used usually in operator<< streaming operators, as in the following example: 

QDBusArgument &operator<<(QDBusArgument &argument, const MyStructure &mystruct)
{
    argument.beginStructure();
    argument << mystruct.member1 << mystruct.member2 << ... ;
    argument.endStructure();
    return argument;
}

Structures can contain other structures, so the following code is also valid: 

QDBusArgument &operator<<(QDBusArgument &argument, const MyStructure &mystruct)
{
    argument.beginStructure();
    argument << mystruct.member1 << mystruct.member2;
    argument.beginStructure();
    argument << mystruct.member3.subMember1 << mystruct.member3.subMember2;
    argument.endStructure();
    argument << mystruct.member4;
    argument.endStructure();
    return argument;
}

另请参阅 endStructure (), beginArray ()，和 beginMap ().

void QDBusArgument:: beginStructure () const

Opens a D-Bus structure suitable for extracting elements.

This function is used usually in operator>> streaming operators, as in the following example: 

const QDBusArgument &operator>>(const QDBusArgument &argument, MyStructure &mystruct)
{
    argument.beginStructure()
    argument >> mystruct.member1 >> mystruct.member2 >> mystruct.member3 >> ...;
    argument.endStructure();
    return argument;
}

另请参阅 endStructure (), beginArray ()，和 beginMap ().

ElementType QDBusArgument:: currentType () const

Returns the classification of the current element type. If an error decoding the type occurs or if we're at the end of the argument, this function returns QDBusArgument::UnknownType .

This function only makes sense when demarshalling arguments. If it is used while marshalling, it will always return UnknownType .

该函数在 Qt 4.5 引入。

void QDBusArgument:: endArray ()

Closes a D-Bus array opened with beginArray (). This function must be called same number of times that beginArray () 被调用。

另请参阅 beginArray (), endStructure ()，和 endMap ().

void QDBusArgument:: endArray () const

Closes the D-Bus array and allow extracting of the next element after the array.

另请参阅 beginArray ().

void QDBusArgument:: endMap ()

Closes a D-Bus map opened with beginMap (). This function must be called same number of times that beginMap () 被调用。

另请参阅 beginMap (), endStructure ()，和 endArray ().

void QDBusArgument:: endMap () const

Closes the D-Bus map and allow extracting of the next element after the map.

另请参阅 beginMap ().

void QDBusArgument:: endMapEntry ()

Closes a D-Bus map entry opened with beginMapEntry (). This function must be called same number of times that beginMapEntry () 被调用。

另请参阅 beginMapEntry ().

void QDBusArgument:: endMapEntry () const

Closes the D-Bus map entry and allow extracting of the next element on the map.

另请参阅 beginMapEntry ().

void QDBusArgument:: endStructure ()

Closes a D-Bus structure opened with beginStructure (). This function must be called same number of times that beginStructure () 被调用。

另请参阅 beginStructure (), endArray ()，和 endMap ().

void QDBusArgument:: endStructure () const

Closes the D-Bus structure and allow extracting of the next element after the structure.

另请参阅 beginStructure ().

void QDBusArgument:: swap ( QDBusArgument & other )

QDBusArgument &QDBusArgument:: operator<< ( uchar arg )

Appends the primitive value arg 类型 BYTE to the D-Bus stream.

QDBusArgument &QDBusArgument:: operator<< ( bool arg )

这是重载函数。

Appends the primitive value arg 类型 BOOLEAN to the D-Bus stream.

QDBusArgument &QDBusArgument:: operator<< ( short arg )

这是重载函数。

Appends the primitive value arg 类型 INT16 to the D-Bus stream.

QDBusArgument &QDBusArgument:: operator<< ( ushort arg )

这是重载函数。

Appends the primitive value arg 类型 UINT16 to the D-Bus stream.

QDBusArgument &QDBusArgument:: operator<< ( int arg )

这是重载函数。

Appends the primitive value arg 类型 INT32 to the D-Bus stream.

QDBusArgument &QDBusArgument:: operator<< ( uint arg )

这是重载函数。

Appends the primitive value arg 类型 UINT32 to the D-Bus stream.

QDBusArgument &QDBusArgument:: operator<< ( qlonglong arg )

这是重载函数。

Appends the primitive value arg 类型 INT64 to the D-Bus stream.

QDBusArgument &QDBusArgument:: operator<< ( qulonglong arg )

这是重载函数。

Appends the primitive value arg 类型 UINT64 to the D-Bus stream.

QDBusArgument &QDBusArgument:: operator<< ( double arg )

这是重载函数。

Appends the primitive value arg 类型 DOUBLE (double-precision floating-point) to the D-Bus stream.

QDBusArgument &QDBusArgument:: operator<< (const QString & arg )

这是重载函数。

Appends the primitive value arg 类型 STRING (Unicode character string) to the D-Bus stream.

QDBusArgument &QDBusArgument:: operator<< (const QDBusVariant & arg )

这是重载函数。

Appends the primitive value arg 类型 VARIANT to the D-Bus stream.

A D-Bus variant type can contain any type, including other variants. It is similar to the Qt QVariant 类型。

QDBusArgument &QDBusArgument:: operator<< (const QStringList & arg )

这是重载函数。

追加 QStringList given by arg as ARRAY of STRING to the D-Bus stream.

QStringList and QByteArray are the only two non-primitive types that are supported directly by QDBusArgument because of their widespread usage in Qt applications.

Other arrays are supported through compound types in Qt D-Bus.

QDBusArgument &QDBusArgument:: operator<< (const QByteArray & arg )

这是重载函数。

追加 QByteArray given by arg as ARRAY of BYTE to the D-Bus stream.

QStringList and QByteArray are the only two non-primitive types that are supported directly by QDBusArgument because of their widespread usage in Qt applications.

Other arrays are supported through compound types in Qt D-Bus.

QDBusArgument &QDBusArgument:: operator= ( QDBusArgument && other )

移动赋值运算符。

QDBusArgument &QDBusArgument:: operator= (const QDBusArgument & other )

拷贝 other QDBusArgument object into this one.

Both objects will therefore contain the same state from this point forward. QDBusArguments are explicitly shared and, therefore, any modification to either copy will affect the other one too.

const QDBusArgument &QDBusArgument:: operator>> ( uchar & arg ) const

Extracts one D-BUS primitive argument of type BYTE from the D-BUS stream and puts it into arg .

const QDBusArgument &QDBusArgument:: operator>> ( bool & arg ) const

这是重载函数。

Extracts one D-Bus primitive argument of type BOOLEAN from the D-Bus stream.

const QDBusArgument &QDBusArgument:: operator>> ( short & arg ) const

这是重载函数。

Extracts one D-Bus primitive argument of type INT16 from the D-Bus stream.

const QDBusArgument &QDBusArgument:: operator>> ( ushort & arg ) const

这是重载函数。

Extracts one D-Bus primitive argument of type UINT16 from the D-Bus stream.

const QDBusArgument &QDBusArgument:: operator>> ( int & arg ) const

这是重载函数。

Extracts one D-Bus primitive argument of type INT32 from the D-Bus stream.

const QDBusArgument &QDBusArgument:: operator>> ( uint & arg ) const

这是重载函数。

Extracts one D-Bus primitive argument of type UINT32 from the D-Bus stream.

const QDBusArgument &QDBusArgument:: operator>> ( qlonglong & arg ) const

这是重载函数。

Extracts one D-Bus primitive argument of type INT64 from the D-Bus stream.

const QDBusArgument &QDBusArgument:: operator>> ( qulonglong & arg ) const

这是重载函数。

Extracts one D-Bus primitive argument of type UINT64 from the D-Bus stream.

const QDBusArgument &QDBusArgument:: operator>> ( double & arg ) const

这是重载函数。

Extracts one D-Bus primitive argument of type DOUBLE (double-precision floating pount) from the D-Bus stream.

const QDBusArgument &QDBusArgument:: operator>> ( QString & arg ) const

这是重载函数。

Extracts one D-Bus primitive argument of type STRING (Unicode character string) from the D-Bus stream.

const QDBusArgument &QDBusArgument:: operator>> ( QDBusVariant & arg ) const

这是重载函数。

Extracts one D-Bus primitive argument of type VARIANT from the D-Bus stream.

A D-Bus variant type can contain any type, including other variants. It is similar to the Qt QVariant 类型。

In case the variant contains a type not directly supported by QDBusArgument , the value of the returned QDBusVariant will contain another QDBusArgument . It is your responsibility to further demarshall it into another type.

const QDBusArgument &QDBusArgument:: operator>> ( QStringList & arg ) const

这是重载函数。

Extracts an array of strings from the D-Bus stream and return it as a QStringList .

QStringList and QByteArray are the only two non-primitive types that are supported directly by QDBusArgument because of their widespread usage in Qt applications.

Other arrays are supported through compound types in Qt D-Bus.

const QDBusArgument &QDBusArgument:: operator>> ( QByteArray & arg ) const

这是重载函数。

Extracts an array of bytes from the D-Bus stream and return it as a QByteArray .

QStringList and QByteArray are the only two non-primitive types that are supported directly by QDBusArgument because of their widespread usage in Qt applications.

Other arrays are supported through compound types in Qt D-Bus.

相关非成员

int qDBusRegisterMetaType ()

注册 T 采用 Qt D-Bus Type System and the Qt meta-type system , if it's not already registered.

To register a type, it must be declared as a meta-type with the Q_DECLARE_METATYPE () macro, and then registered as in the following example: 

#include <QDBusMetaType>
qDBusRegisterMetaType<MyClass>();

若 T isn't one of Qt's 容器类 ， operator<< and operator>> streaming operators between T and QDBusArgument must be already declared. See the Qt D-Bus Type System page for more information on how to declare such types.

This function returns the Qt meta type id for the type (the same value that is returned from qRegisterMetaType ()).

注意： The feature that a T inheriting a streamable type (including the containers QList , QHash or QMap ) can be streamed without providing custom operator<< and operator>> is deprecated as of Qt 5.7, because it ignores everything in T except the base class. There is no diagnostic. You should always provide these operators for all types you wish to stream and not rely on Qt-provided stream operators for base classes.

注意： 此函数是 thread-safe .

该函数在 Qt 4.2 引入。

另请参阅 Qt D-Bus Type System , qRegisterMetaType ()，和 QMetaType .

T qdbus_cast (const QDBusArgument & argument )

Attempts to demarshall the contents of argument into the type T 。例如： 

MyType item = qdbus_cast<Type>(argument);

Note that it is equivalent to the following: 

MyType item;
argument >> item;

该函数在 Qt 4.2 引入。