Mapping onto an existing object with children #1310

jpbertles · 2024-05-28T14:34:14Z

jpbertles
May 28, 2024

First off, I just want to say that this is an awesome library. Really great work on this!

I have a situation where I have a Customer object that has an Address. I would like to map onto an existing customer and for the customer specific properties everything is working great, but the auto generated code always creates a new address object, and doesn't map onto the existing one. Is there anything I can do to ensure the existing address object is mapped onto rather than creating a new one?

public class Customer
{
    public Guid CustomerId { get; set; }
    public string Name { get; set; }
    ...
    public Address Address { get; set; }
}

public class Address
{
    public Guid AddressId { get; set; }
    public string Street1 { get; set; }
    ....
}

public class CustomerDto
{
    public string Name { get; set; }
    ...
    public AddressDto Address { get; set; }
}

public class AddressDto
{
    public string Street1 { get; set; }
    ....
}

[Mapper]
public static partial CustomerMapper
{
    public static partial void MapUpdateOntoDbModel(CustomerDto dto, Customer customer);
}


/// This is the generated code
public static partial class CustomerMapper
{
    [global::System.CodeDom.Compiler.GeneratedCode("Riok.Mapperly", "3.5.1.0")]
    public static partial void MapUpdateOntoDbModel(global::CustomerDto dto, global:Customer customer)
    {
        if (dto.Address != null)
        {
            customer.Address = MapToAddress1(dto.Address);
        }
        else
        {
           customer.Address = null;
        }
        ....
    }
}

latonz · 2024-05-28T22:35:11Z

latonz
May 28, 2024
Maintainer

Created #1311

0 replies

ste4net · 2024-09-10T22:14:30Z

ste4net
Sep 10, 2024

I think there's something I'm missing because this request doesn't seem to have the audience I expected, so I don't understand how others handle enumerable properties.

All my List<T> properties need to always be managed with updates. If the source has new elements, I add them; if the target has extra elements compared to the source, I remove them, and for the rest, I update them. The comparison is based on the unique key of the element.

I don't see any other way this could be managed.
@jpbertles Are you using Mapperly? If so, how do you handle this situation?

3 replies

latonz Sep 11, 2024
Maintainer

How does your manually written code look like to achieve this? This sound quite complex and I'm not sure if a general object to object mapper is the right place to do complex merging operations. May also be related to #665.

ste4net Sep 12, 2024

Yes it is related to #665 I would use an approach like the one I’ve written below (done quickly and not optimized, just as an example).
But I imagine I could solve the list mapping by implementing a generic method on the base class (it's related to post 234).
However, the main problem is that the mapping between existing objects in the case of lists always creates a new list, or it expects custom methods to create a new list instead of a mapping method that accepts the existing list.

        public void MapExisting(Company src, CompanyViewModel dst)
         {

            //...
            //if (dst.Addresses == null) dst.Addresses = new List<AddressVM>(); //Redoundat if initialized in constructor
            MapToList(src.Addresses, dst.Addresses, (x, y) => x.Id == y.Id);
        }
        public void MapListElemtxy<T1, T2>(T1 src, T2 dst)
        {
            //...
        }
        public void MapToList<T, T2>(List<T> Src, List<T2> Dst, Func<T, T2, bool> predicate) where T : class, IDomainEntity where T2 : class, IDomainEntity, new()
        {
            // Remove all items from Dst not in Src
            Dst.RemoveAll(x => !Src.Any(y => y.Id == x.Id));
            foreach (var item in Src)
            {
                T2 AddOrUpd = Dst.FirstOrDefault(d => d.Id == item.Id, new T2());
                MapListElemtxy(item, AddOrUpd);
                if (AddOrUpd.Id == 0) Dst.Add(AddOrUpd);
            }
        }

Now mapperly produce this ...

        [global::System.CodeDom.Compiler.GeneratedCode("Riok.Mapperly", "3.6.0.0")]
        public partial void DomainToVm(global::BizWork.LohiCore.Domain.MBase.Company domain, global::LohiCore.Server.ViewModels.CompanyViewModel vm)
        {
            if (domain.Addresses != null)
            {
                vm.Addresses = MapToListOfAddress(domain.Addresses);
            }
            else
            {
                vm.Addresses = null;
            }

Instead when we are mapping between existng object it should be something like

 MapToListOfExistingAddress(domain.Addresses,vm.Addresses);
Or
MapToListOfExistngItems<T,T2>(domain.Addresses,vm.Addresses);

Just to have the possibility of implementing the list update if it is considered too specific a case to be implemented in the mapper

latonz Sep 16, 2024
Maintainer

This is tracked in #451

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

Uh oh!

Mapping onto an existing object with children #1310

Uh oh!

{{title}}

Uh oh!

Uh oh!

{{editor}}'s edit

{{editor}}'s edit

Uh oh!

Replies: 2 comments 3 replies

Uh oh!

{{title}}

Uh oh!

Uh oh!

{{title}}

Uh oh!

Uh oh!

{{title}}

Uh oh!

Uh oh!

{{title}}

Uh oh!

Uh oh!

{{editor}}'s edit

{{editor}}'s edit

Uh oh!

Uh oh!

{{title}}

Uh oh!

Select a reply

Uh oh!

Uh oh!

Uh oh!

Mapping onto an existing object with children #1310

Uh oh!

Uh oh!

jpbertles May 28, 2024

Replies: 2 comments · 3 replies

Uh oh!

latonz May 28, 2024 Maintainer

Uh oh!

ste4net Sep 10, 2024

Uh oh!

latonz Sep 11, 2024 Maintainer

Uh oh!

Uh oh!

ste4net Sep 12, 2024

Uh oh!

latonz Sep 16, 2024 Maintainer

jpbertles
May 28, 2024

Replies: 2 comments 3 replies

latonz
May 28, 2024
Maintainer

ste4net
Sep 10, 2024

latonz Sep 11, 2024
Maintainer

latonz Sep 16, 2024
Maintainer