If you need a field which is "an int32 value, or not set" you can use the
google.protobuf.Int32Value message type.
In proto file,Which field type I can use?
在 2015年7月17日星期五 UTC+8下午9:10:29，Jon Skeet写道：
>
> On Friday, 17 July 2015 02:34:21 UTC+1, Wu XIANG wrote:
>>
>>
>> Is it true that has methods for optional fields in proto3 are removed
>> from generated message ?
>>
>
> For primitive types, yes.
>
>
>> If so, how can I decide if this field has been set or not ?
>>
>
> You can't. An int32 field that's been set to 0 is exactly the same as an
> int32 field that hasn't been set at all.
>
> (For oneofs, you could still tell that it was the int32 field that was
> set, so that's slightly difference.)
>
> From the documentation:
>
> > Note that for scalar message fields, once a message is parsed there's no
> way of telling whether a field was explicitly set to the default value (for
> example whether a boolean was set to false) or just not set at all: you
> should bear this in mind when defining your message types.
>
> If you need a field which is "an int32 value, or not set" you can use the
> google.protobuf.Int32Value message type.
>
> Jon
>
>
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