Re: [protobuf] Re: Message.getField(FieldDescriptor) and enum values.
Are there any other thoughts on this? We would like to write some methods
that operate generically on fields. Solutions such as the one Ben points
out force the code for enums differ from the code for all other field types.
We can fake it when assigning fields from a value (the EnumValueDescriptor
is accessible from an enum instance), but there does not appear to be a way
to go from an EnumValueDescriptor to an enum value *that does not rely on
calling static methods.*
*
*
*-- Jim
*
On Mon, May 23, 2011 at 6:40 PM, Ben Wright compuware...@gmail.com wrote:
If that's all you're trying to do, you don't really need the java enum
value...
The EnumValueDescriptor is what you use for the value when calling
setField(FieldDescriptor field, Object value) for an Enum Field
On May 23, 5:09 pm, Jim Mayer j...@pentastich.org wrote:
That's exactly the problem. We don't. This issue first came up for us
when
writing code to copy data from one subtree to another of a protocol
buffer.
By passing in a field descriptor we were able to eliminate a LOT of
duplicated code. In that case, we only needed the field access to write
and
so were able to get the descriptor. We anticipate the same issue coming
up
for reading, however.
We could define an interface with a 'get' and a 'set' method and avoid
using
getField/setField at all, but it seems unfortunate that the capability
isn't
in the API. The data appears to all be there; in fact, it appears that
GeneratedMessage.SingularEnumFieldAccessor adds extra code to get the
current behavior.
-- Jim
On Mon, May 23, 2011 at 4:37 PM, Ben Wright compuware...@gmail.com
wrote:
Assuming you know the Java Enum Type for which the EnumValueDescriptor
is describing a type of...
MyJavaEnum.valueOf((EnumValueDescriptor)value)
will return the appropriate java enum value.
On May 23, 1:42 pm, Jim Mayer j...@pentastich.org wrote:
In the Java protocol buffer binding, is there a way to get the Java
enum value using protocol buffer reflection? Specifically, I'd like
to be able to write something like the following:
Object getFieldValue(MessageOrBuilder source, FieldDescriptor
field)
{
Object value = source.getField(field);
if (value instanceof EnumValueDescriptor) {
return the Java enum corresponding to the descriptor;
} else {
return value;
}
}
As far as I can tell, this isn't possible as the methods that return
enums from the descriptors are all static on the enum class. Since
they are static, there is no way (short of reflection games) to
invoke
them unless one has the class in hand. I would enjoy being proved
wrong :-)
What we'd really like to see is an easy mechanism that would give us
the following:
Something explicitValue = message.getXXX();
Object reflectionValue =
message.getTheJavaValueFromAFieldDescriptor(the field descriptor for
XXX);
assert explictValue == reflectionValue;
Similarly, we'd like to be able do the same thing for 'setXXX'
methods
for builders, however in this case it's easy to go from an enum value
to its descriptor so we can get by with the 'setField' method.
Thanks!
-- Jim
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[protobuf] Message.getField(FieldDescriptor) and enum values.
In the Java protocol buffer binding, is there a way to get the Java
enum value using protocol buffer reflection? Specifically, I'd like
to be able to write something like the following:
Object getFieldValue(MessageOrBuilder source, FieldDescriptor field)
{
Object value = source.getField(field);
if (value instanceof EnumValueDescriptor) {
return the Java enum corresponding to the descriptor;
} else {
return value;
}
}
As far as I can tell, this isn't possible as the methods that return
enums from the descriptors are all static on the enum class. Since
they are static, there is no way (short of reflection games) to invoke
them unless one has the class in hand. I would enjoy being proved
wrong :-)
What we'd really like to see is an easy mechanism that would give us
the following:
Something explicitValue = message.getXXX();
Object reflectionValue =
message.getTheJavaValueFromAFieldDescriptor(the field descriptor for
XXX);
assert explictValue == reflectionValue;
Similarly, we'd like to be able do the same thing for 'setXXX' methods
for builders, however in this case it's easy to go from an enum value
to its descriptor so we can get by with the 'setField' method.
Thanks!
-- Jim
--
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Re: [protobuf] Re: Message.getField(FieldDescriptor) and enum values.
That's exactly the problem. We don't. This issue first came up for us when
writing code to copy data from one subtree to another of a protocol buffer.
By passing in a field descriptor we were able to eliminate a LOT of
duplicated code. In that case, we only needed the field access to write and
so were able to get the descriptor. We anticipate the same issue coming up
for reading, however.
We could define an interface with a 'get' and a 'set' method and avoid using
getField/setField at all, but it seems unfortunate that the capability isn't
in the API. The data appears to all be there; in fact, it appears that
GeneratedMessage.SingularEnumFieldAccessor adds extra code to get the
current behavior.
-- Jim
On Mon, May 23, 2011 at 4:37 PM, Ben Wright compuware...@gmail.com wrote:
Assuming you know the Java Enum Type for which the EnumValueDescriptor
is describing a type of...
MyJavaEnum.valueOf((EnumValueDescriptor)value)
will return the appropriate java enum value.
On May 23, 1:42 pm, Jim Mayer j...@pentastich.org wrote:
In the Java protocol buffer binding, is there a way to get the Java
enum value using protocol buffer reflection? Specifically, I'd like
to be able to write something like the following:
Object getFieldValue(MessageOrBuilder source, FieldDescriptor field)
{
Object value = source.getField(field);
if (value instanceof EnumValueDescriptor) {
return the Java enum corresponding to the descriptor;
} else {
return value;
}
}
As far as I can tell, this isn't possible as the methods that return
enums from the descriptors are all static on the enum class. Since
they are static, there is no way (short of reflection games) to invoke
them unless one has the class in hand. I would enjoy being proved
wrong :-)
What we'd really like to see is an easy mechanism that would give us
the following:
Something explicitValue = message.getXXX();
Object reflectionValue =
message.getTheJavaValueFromAFieldDescriptor(the field descriptor for
XXX);
assert explictValue == reflectionValue;
Similarly, we'd like to be able do the same thing for 'setXXX' methods
for builders, however in this case it's easy to go from an enum value
to its descriptor so we can get by with the 'setField' method.
Thanks!
-- Jim
--
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