I'm working on a project with vibe.d and ddbc to access my database.
Both have powerful functions that operate on Struct types to avoid a lot of boilerplate code.
I have a web site that sends a json message to update a record.
deserializeJson creates a new Foo record containing the json data.
However, there are some fields in the record which are not in the json, and these get default values.
I have another Foo that has the original values.

What would be the best way to merge the updated values into the original?
Obviously I can copy from one Foo to the other, but that's pretty inelegant.
If I could pass an existing Foo to deserializeJson and have only some fields filled in, that would be perfect.
I tried this:

deserializeJson!Foo(foo, req.json);

but it completely overwrites all the fields in foo.

Any suggestions? Is there a trick I'm just not seeing?

--
Chris

On 2/12/21 6:22 PM, Chris Bare wrote:
> I'm working on a project with vibe.d and ddbc to access my database.
> Both have powerful functions that operate on Struct types to avoid a lot of boilerplate code.
> I have a web site that sends a json message to update a record.
> deserializeJson creates a new Foo record containing the json data.
> However, there are some fields in the record which are not in the json, and these get default values.
> I have another Foo that has the original values.
> 
> What would be the best way to merge the updated values into the original?
> Obviously I can copy from one Foo to the other, but that's pretty inelegant.
> If I could pass an existing Foo to deserializeJson and have only some fields filled in, that would be perfect.
> I tried this:
> 
> deserializeJson!Foo(foo, req.json);
> 
> but it completely overwrites all the fields in foo.
> 
> Any suggestions? Is there a trick I'm just not seeing?

Does @ignore work? That's a UDA that tells vibe to ignore the field. Though I don't know if it means it leaves it alone completely.

https://vibed.org/api/vibe.data.serialization/ignore

-Steve

On Saturday, 13 February 2021 at 01:21:56 UTC, Steven Schveighoffer wrote:
> On 2/12/21 6:22 PM, Chris Bare wrote:
>> [...]
>
> Does @ignore work? That's a UDA that tells vibe to ignore the field. Though I don't know if it means it leaves it alone completely.
>
> https://vibed.org/api/vibe.data.serialization/ignore
>
> -Steve

@ignore just prevents it from throwing an error if the field is not in the json. The field still gets overwritten with it's default value in the struct.