Here the part in the modbus.mspec I was talking about:
[discriminatedType 'ModbusPDU' [bit 'response']
[discriminator bit 'error']
[discriminator uint 7 'function']
[typeSwitch 'error','function','response'
['true' ModbusPDUError
[simple uint 8 'exceptionCode']
]
// Bit Access
['false','0x02','false' ModbusPDUReadDiscreteInputsRequest
[simple uint 16 'startingAddress']
[simple uint 16 'quantity']
]
['false','0x02','true' ModbusPDUReadDiscreteInputsResponse
[implicit uint 8 'byteCount' 'COUNT(value)']
[array int 8 'value' count 'byteCount']
]
So the input values in the "typeSwitch" are actually expressions that are
evaluated. It doesn't really care about if something's a discriminator.
A discriminator is only interesting when serializing as in this case it doesn't
store the value in the pojo but gets the value from the type instead.
Chris
Am 26.08.20, 10:29 schrieb "Christofer Dutz" <[email protected]>:
Hi Lukasz,
It would be pretty simple to extend the code generation to make the virtual
fields available in the parser ...
I just didn't do it as I then didn't see the need. Should be extremely
simple to implement. (Sort of just a copy+paste of the pojo template)
You can use type-arguments in typeSwitches ... just have a look at the
modbus mspec.
What do you mean with "undeclared discriminators"?
Chris
Am 26.08.20, 01:22 schrieb "Łukasz Dywicki" <[email protected]>:
I been trying to write new mspecs and I found that discriminator
handling is quite limiting in current form.
For example it is possible to declare a type argument, but it is not
possible to use it as a divider.
It is also not possible to use a virtual or manual field as a
discriminator which could very well be source for type information. I am
aware that virtual field is computed at runtime with given expression.
I am not entirely sure of all implications for changing the handling.
Currently discriminator is a simple field which gets registered in
discriminator set.
What do you think about making a `discriminator` rather an modifier
which could be placed for type arguments and also in other places? At
the moment any use of [typeSwitch] with undeclared discriminator causes
null pointers in freemarker templates and failure.
Cheers,
Łukasz
