[SOLVED] protoRPC: returning dict

protoRPC: returning dict

How does one return a dict like object through protoRPC ?

I tried using the FieldList to no avail. I only see the following field definitions:

       'IntegerField',
       'FloatField',
       'BooleanField',
       'BytesField',
       'StringField',
       'MessageField',
       'EnumField',

Solution

There are two scenarios:

1) Your dict has a well-defined schema: This is the best use case for ProtoRPC and if possible you should try to fit it into a schema. In this case, you would use a MessageField with some Message class that matches the schema in your dictionary.

For example, instead of

{'amount': 31, 'type': 'fish', mine: False}

you could define

from protorpc import messages
class MyCatch(messages.Message):
  amount = messages.IntegerField(1)
  type = messages.StringField(2)
  mine = messages.BooleanField(3)

and then use this message definition in a field via

messages.MessageField(MyCatch, index, ...)

2) Your dict does not have a well-defined schema: In this case you can use json to dump your dictionary to a string and request ensure_ascii=True to make sure the return type is a bytes (str) object. Then you can just use a BytesField.

For example:

import json

class MyMessage(messages.Message):
   some_dict = messages.BytesField(1)

my_dict = {'amount': 31, 'type': 'fish', mine: False}
message = MyMessage(some_dict=json.dumps(my_dict, ensure_ascii=True))

The use of ensure_ascii is optional as True is the default, but this may change depending on your environment.

Instead you could use pickle to serialize your dictionary. The method pickle.dumps always outputs ASCII/binary, so by swapping out json.dumps for pickle.dumps and dropping the ensure_ascii=True, you'd have the same outcome.