Global registration of type converters

[thrixton]

I have an IPropertyConverter from NodaTime.ZonedDatetime to string
I can register this either via DynamoDBPropertyAttribute or AWSConfigsDynamoDB.Context.AddMapping as illustrated here
This works ok but is repetitive and error prone

Is it possible to globally register a type converter?
e.g (imagined) AWSConfigsDynamoDB.Context.AddTypeMapping<ZonedDatetime, ZonedDateTimeConverter>()

[ashishdhingra]

Hi @thrixton,

Good morning.

I understand your concern and correct me if I'm wrong, instead of configuring type converter individually for several tables, you would like to use a global mapping for all the tables. Based on information available in the documentation, I'm not sure if that is possible. Example Mapping Arbitrary Data with DynamoDB Using the AWS SDK for .NET Object Persistence Model also applies type converter to specific table. Looking at the codebase, TypeMapping is tied to a specific target table, hence the limitation. Hope this helps.

Thanks,
Ashish

[thrixton]

Hi @ashishdhingra,
Thanks for the reply.
It does seem very tied to a particular table, which seems odd to me from a design perspective given that in most (all?) of my experience I've wanted to serialize a particular type in a standard way instead of a particular way dependent on the "container" type.
Is there any particular reason why a mapping should be tied to a table?
In you opinion would it be easy or acceptable to add a mechanism to add a global type mapping?
I'd be happy to put a PR together if it would help.

[ashishdhingra]

Hi @thrixton,

I'm not sure about the actual design on why mapping would be tied to a particular table. Just curious, do you happen to see similar feature in another AWS SDK (e.g. Java)? Feel free to contribute PR. I would mark this issue as a feature-request.

Thanks,
Ashish

[rhullah]

I kind of want something like this too, but a little different. The want to define a Converter on the root object stored in the table. I have a that table stores the children of an inherited type and want to return the child types. So I'd like to define a Converter that knows how to read the data in the table and return the specific child type.

As an example, I have an Animal parent class and two child classes, Cat and Dog which inherit from Animal. I want to be able to define a converter on the Animal class that knows how to look at the data and return the proper child class. That way I can just query an Animal and get either Cat or Dog and not have to query the Animal table as a Document and then call another function that does the translation for me.

[ffMathy]

I am interested in this, and don't need per-table mappings. A global one would suffice.

[jamescarter-le]

I also have this problem, I want to use a .NET Type System.Numerics.BigInteger and register a type converter so I can use it as follows:

public Dictionary<string, Dictionary<string, BigInteger>> AddressTokenMovements { get; set; } = new();

Currently I cannot serialize this object, because I cannot add a PropertyConverter to the type, as it is not in my codebase, and cannot globally register the type/converter.