On Thursday, 2 June 2022 at 08:27:32 UTC, Antonio wrote:
JSON properties can be
- a value
- null
- absent
What's the standard way to define a serialziable/deserializable
structs supporting properties of any of this 4 kinds?:
* int
* int | null
* int | absent
* int | null | absent
Whats the best library to manage this JSON requirements? (all
the 4 cases)?
Thanks
null and absent should be treated the same in the code, it's only
when serializing you should define one or the other, if you need
to have null values AND absent values then attributing
accordingly is the solution.
Which means deserialization only has value/null and serialization
has value/null by default, but can be opt-in to also have absent.
One common mistake I've seen with parsers in D is that fields are
often opt-out, instead of opt-in, which means you always have to
declare all fields in a json object, but that's a bad
implementation. All fields should be optional and only required
when attributed.
An example:
```
struct A { int x; }
```
Should be able to be deserialized from this json:
```
{"x":100,"y":200}
```
However a lot of parsers in D do not support that. Instead you
must declare the y member as well like:
```
struct A { int x; int y; }
```
Any decent parser should not have that problem.
If a field is required then it should be determined by an
attribute like:
```
struct A {
@JsonRequired int x;
@JsonRequired int y;
}
```
If that attribute isn't present then it can be absent during
deserialization.
Sorry I got a little off-track, but I felt like pointing these
things out are important as well.
