Mapping a list of classes to a list of id's

[Sune1337]

I would like to map a list of classes to a list of id's, but can't really figure out how to do this with Mapperly.
Currently my workaround is to use before/after mapping; but i do think i will hit issues when combining this with IQueryable mapping for use with Entityframework core.

Example: I want to map Parent to ParentDto, and Children should be mapped to ChildIds.

public class Child
{
    public long Id { get; set; }
}

public class Parent
{
    public IEnumerable<Child> Children { get; set; }
}

public class ParentDto
{
    public IEnumerable<long> ChildIds { get; set; }
}

[TimothyMakkison]

Hey, I think this can be solved with a user implemented mapper.

[Mapper]
public static partial class ParentMapper
{
  public static partial ParentDto MapParent(Parent source);
  
  public static long ChildToLong(Child source) => source.Id;
}

[Sune1337]

That mapper generated this code for me, so it didnt work at first try; but i do agree it looks like it should work. Gonna keep experiment with it abit.

    public static partial class ParentMapper
    {
        public static partial global::LicensePlateAPIv1.Mappers.ParentDto MapParent(global::LicensePlateAPIv1.Mappers.Parent source)
        {
            var target = new global::LicensePlateAPIv1.Mappers.ParentDto();
            return target;
        }
    }

[TimothyMakkison]

Sorry didn't see that your members have different name 😅. You can solve this by adding a MapProperty attribute.

[Mapper]
public static partial class ParentMapper
{
    [MapProperty(nameof(Parent.Children), nameof(ParentDto.ChildIds))]
    public static partial ParentDto MapParent(Parent source);
  
    public static long ChildToLong(Child source) => source.Id;
}

// generates
 public static partial global::ParentDto MapParent(global::Parent source)
{
    var target = new global::ParentDto();
    target.ChildIds = global::System.Linq.Enumerable.Select(source.Children, x => ChildToLong(x));
    return target;
}

[Sune1337]

That works for me, Thank you so much!