Setting a target's required nullable property to a default value when the source doesn't have a property

[sander1095]

Hello!

Apologies for the confusing title. The code will be a lot clearer.

My target class has a required, nullable property but the source doesn't have a property for this.

I can not figure out how to make mapperly work with this. In this case, I want to be able to configure mapperly to set it to the default value.

public class Source
{
    public required string Text { get; set; }
}

public class Target
{
    public required string? Id { get; set; }
    public required string Text { get; set; }
}

[Mapper]
public static partial class Mapper
{
    // TODO: How can I tell Mapperly to initialize Target.Id with its default value (null)?
    // I do not have a value to map from!
    public static partial Target Map(this Source source);
}

Thanks!

[latonz]

Mapperly 4.0 introduces MapValue which is exactly what you need here. You can try it out with the latest version of Mapperly from the next channel 4.0.0-next.1. See the docs. In your case it should work by applying [MapValue(nameof(Target.Id), null)] to the Map method.

Note that this is a prerelease and it may break its API with any release.