内容

• 特性
• 公共函数
• 详细描述

QMqttMessage Class

The QMqttMessage class provides information about a message received from a message broker based on a subscription. 更多...

头：	#include <QMqttMessage>
qmake:	QT += mqtt

• 所有成员列表，包括继承成员

特性

duplicate : const bool id : const quint16 payload : const QByteArray

qos : const quint8 retain : const bool topic : const QMqttTopicName

公共函数

	QMqttMessage (const QMqttMessage & other )
	QMqttMessage ()
QMqttMessage &	operator= (const QMqttMessage & other )
bool	duplicate () const
quint16	id () const
const QByteArray &	payload () const
QMqttPublishProperties	publishProperties () const
quint8	qos () const
bool	retain () const
QMqttTopicName	topic () const
bool	operator!= (const QMqttMessage & other ) const
bool	operator== (const QMqttMessage & other ) const

详细描述

An MQTT message is created inside the module and returned via the QMqttSubscription::messageReceived () 信号。

特性文档编制

[read-only] duplicate : const bool

This property holds whether the message is a duplicate.

Duplicate messages indicate that the message has been sent earlier, but it has not been confirmed yet. Hence, the broker assumes that it needs to resend to verify the transport of the message itself. Duplicate messages can only occur if the QoS level is one or two.

访问函数：

bool	duplicate () const

[read-only] id : const quint16

This property holds the ID of the message.

IDs are used for messages with a QoS level above zero.

访问函数：

quint16

id () const

[read-only] payload : const QByteArray

This property holds the payload of a message.

访问函数：

const QByteArray &

payload () const

[read-only] qos : const quint8

This property holds the QoS level of a message.

访问函数：

quint8

qos () const

[read-only] retain : const bool

This property holds whether the message has been retained.

A retained message is kept on the broker for future clients to subscribe. Consequently, a retained message has been created previously and is not a live update. A broker can store only one retained message per topic.

访问函数：

bool	retain () const

[read-only] topic : const QMqttTopicName

This property holds the topic of a message.

In case a wildcard has been used for a subscription, describes the topic matching this subscription. This property never contains wildcards.

访问函数：

QMqttTopicName

topic () const

成员函数文档编制

QMqttMessage:: QMqttMessage (const QMqttMessage & other )

Constructs a new MQTT message that is a copy of other .

QMqttMessage:: QMqttMessage ()

Creates a new MQTT message.

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

Makes this object a copy of other and returns the new value of this object.

[since 5.12] QMqttPublishProperties QMqttMessage:: publishProperties () const

Returns the publish properties received as part of the message.

注意： This function only specifies the properties when a publish message is received. Messages with a QoS value of 1 or 2 can contain additional properties when a message is released. Those can be obtained by the QMqttClient::messageStatusChanged 信号。

注意： This function will only provide valid data when the client specifies QMqttClient::MQTT_5_0 as QMqttClient::ProtocolVersion .

该函数在 Qt 5.12 引入。

bool QMqttMessage:: operator!= (const QMqttMessage & other ) const

返回 true if the message and other are not equal, otherwise returns false .

bool QMqttMessage:: operator== (const QMqttMessage & other ) const

返回 true if the message and other 相等，否则返回 false .