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 |
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 |
An MQTT message is created inside the module and returned via the QMqttSubscription::messageReceived () 信号。
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 |
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 |
This property holds the payload of a message.
访问函数:
const QByteArray & | payload () const |
This property holds the QoS level of a message.
访问函数:
quint8 | qos () const |
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 |
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 |
Constructs a new MQTT message that is a copy of other .
Creates a new MQTT message.
Makes this object a copy of other and returns the new value of this object.
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。
返回
true
if the message and
other
are not equal, otherwise returns
false
.
返回
true
if the message and
other
相等,否则返回
false
.