protobuf messages as repeated field?

[Lotte R. Leben]

Hi,

this might be quite the newbie question, but I haven't been able to find any hints through googling, so here it goes:

What I'm trying to to is send orotobuf messages between an Android App a Python Script containing (among other things) a list of key-value pairs (if ints). 

The solution that I came up with was just defining my own “tuple” as another protobuf message and then including a repated field of said type, like so:

message CheckMessage {

message BalanceUpdateMessage{

required int32 transactionID = 1;

required sint32 amount = 2;

}

required int32 amount = 3;

required sint32 newBalance = 5;

repeated BalanceUpdateMessage balanceUpdates = 4;

}  

and then try to fill the balaceUpdates in Python (the checkMessages are embedded in another packetMessage):

        balanceUpdateMessage = protoPackets_pb2.CheckMessage.BalanceUpdateMessage()

        balanceUpdateMessage.transactionID = 1111

        balanceUpdateMessage.amount = 2222

        packetMessage.checkMessage.balanceUpdates.append(balanceUpdateMessage)

But when I run this, I get the error:

AttributeError: 'RepeatedCompositeFieldContainer' object has no attribute 'append'

... I kind of expected my approach to fail, but not with an error message like this :D

So my question is: Is it even possible to send multiple key,value - pairs with protobuf and if yes, how? Or if I'm on the right track: what is my mistake? 

( I know that one usually would set the contents of a “nested” message with packetMessage.checkMessage.balanceUpdateMessage.transactionID = 333 (or so), but since I'm dealing with a repeated field that neither works nor would it make sense (to me, at least). )

[Ilia Mirkin]

Try

x = packetMessage.checkMessage.balanceUpdates.add()
x.tid = 111
x.amount = 222

See https://developers.google.com/protocol-buffers/docs/pythontutorial
for more info.

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[Lotte R. Leben]

Hi Ilia,

Am Montag, 24. Juni 2013 20:26:47 UTC+2 schrieb Ilia Mirkin:

Try

x = packetMessage.checkMessage.balanceUpdates.add()
x.tid = 111
x.amount = 222

works like a charm, thank you so much!

[Mingjian Lu]

For anyone who might reach here for the same question. I suggest using extend instead of add and then give values to fields.  For example:

packetMessage.checkMessage.balanceUpdates.extend([balanceUpdateMessage])

This is much simpler and also easy for assigning object after deserialization and nested structures.