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# QDBusPendingReply Class Reference
[QtDBus module]

The QDBusPendingReply class contains the reply to an asynchronous method call More...

Inherits QDBusPendingCall.

### Methods

- __init__ (self)
- __init__ (self, QDBusPendingReply other)
- __init__ (self, QDBusPendingCall call)
- __init__ (self, QDBusMessage reply)
- QVariant argumentAt (self, int index)
- QDBusError error (self)
- bool isError (self)
- bool isFinished (self)
- bool isValid (self)
- QDBusMessage reply (self)
- object value (self, object type = None)
- waitForFinished (self)

## Detailed Description

The QDBusPendingReply class contains the reply to an asynchronous method call

The QDBusPendingReply is a template class with up to 8 template parameters. Those parameters are the types that will be used to extract the contents of the reply's data.

This class is similar in functionality to QDBusReply, but with two important differences:

- QDBusReply accepts exactly one return type, whereas QDBusPendingReply can have from 1 to 8 types
- QDBusReply only works on already completed replies, whereas QDBusPendingReply allows one to wait for replies from pending calls

Where with QDBusReply you would write:

     QDBusReply<QString> reply = interface->call("RemoteMethod");
     if (reply.isValid())
         // use the returned value
         useValue(reply.value());
     else
         // call failed. Show an error condition.
         showError(reply.error());

with QDBusPendingReply, the equivalent code (including the blocking wait for the reply) would be:

         QDBusPendingReply<QString> reply = interface->asyncCall("RemoteMethod");
         reply.waitForFinished();
         if (reply.isError())
             // call failed. Show an error condition.
             showError(reply.error());
         else
             // use the returned value
             useValue(reply.value());

For method calls that have more than one output argument, with QDBusReply, you would write:

     QString reply = interface->call("RemoteMethod");

whereas with QDBusPendingReply, all of the output arguments should be template parameters:

         QDBusPendingReply<bool, QString> reply = interface->asyncCall("RemoteMethod");
         reply.waitForFinished();
         if (!reply.isError()) {
             if (reply.argumentAt<0>())
                 showSuccess(reply.argumentAt<1>());
             else
                 showFailure(reply.argumentAt<1>());
         }

QDBusPendingReply objects can be associated with QDBusPendingCallWatcher objects, which emit signals when the reply arrives.

## Method Documentation

### QDBusPendingReply.__init__ (self)

Creates an empty QDBusPendingReply object. Without assigning a QDBusPendingCall object to this reply, QDBusPendingReply cannot do anything. All functions return their failure values.

### QDBusPendingReply.__init__ (self, QDBusPendingReply other)

Creates a copy of the other QDBusPendingReply object. Just like QDBusPendingCall and QDBusPendingCallWatcher, this QDBusPendingReply object will share the same pending call reference. All copies share the same return values.

### QDBusPendingReply.__init__ (self, QDBusPendingCall call)

Creates a QDBusPendingReply object that will take its contents from the call pending asynchronous call. This QDBusPendingReply object will share the same pending call reference as call.

### QDBusPendingReply.__init__ (self, QDBusMessage reply)

Creates a QDBusPendingReply object that will take its contents from the message message. In this case, this object will be already in its finished state and the reply's contents will be accessible.

See also isFinished().

### QVariant QDBusPendingReply.argumentAt (self, int index)

Returns the argument at position index in the reply's contents. If the reply doesn't have that many elements, this function's return value is undefined (will probably cause an assertion failure), so it is important to verify that the processing is finished and the reply is valid.

### QDBusError QDBusPendingReply.error (self)

Retrieves the error content of the reply message, if it has finished processing. If the reply message has not finished processing or if it contains a normal reply message (non-error), this function returns an invalid QDBusError.

### bool QDBusPendingReply.isError (self)

Returns true if the reply contains an error message, false if it contains a normal method reply.

If the pending call has not finished processing, this function also returns true.

### bool QDBusPendingReply.isFinished (self)

Returns true if the pending call has finished processing and the reply has been received. If this function returns true, the isError(), error() and reply() methods should return valid information.

Note that this function only changes state if you call waitForFinished() or if an external D-Bus event happens, which in general only happens if you return to the event loop execution.

See also QDBusPendingCallWatcher.isFinished().

### bool QDBusPendingReply.isValid (self)

Returns true if the reply contains a normal reply message, false if it contains anything else.

If the pending call has not finished processing, this function return false.

### QDBusMessage QDBusPendingReply.reply (self)

Retrieves the reply message received for the asynchronous call that was sent, if it has finished processing. If the pending call is not finished, this function returns a QDBusMessage of type QDBusMessage.InvalidMessage.

After it has finished processing, the message type will either be an error message or a normal method reply message.

### object QDBusPendingReply.value (self, object type = None)

Returns the first argument in this reply, cast to type `T1` (the first template parameter of this class). This is equivalent to calling argumentAt<0>().

This function is provided as a convenience, matching the QDBusReply.value() function.

Note that, if the reply hasn't arrived, this function causes the calling thread to block until the reply is processed.

### QDBusPendingReply.waitForFinished (self)

Suspends the execution of the calling thread until the reply is received and processed. After this function returns, isFinished() should return true, indicating the reply's contents are ready to be processed.

See also QDBusPendingCallWatcher.waitForFinished().