Mapping nullable Enum to custom object

[WahidBitar]

for now I can have something like the following to register mapping for all enums in the system

config.NewConfig<Enum, KeyValueData>()
            .MapWith(s => new KeyValueData(s, Enums.ResourceManager));

However, it's not possible to have the same cofig for a nullable Enum.

The following config is not working:

config.NewConfig<Enum?, KeyValueData?>()
            .MapWith(s => s == null ? null : new KeyValueData(s.ToString(), Enums.ResourceManager));

I'll get the following Exception

Error while compiling
source=Tests.FirstClass
destination=Tests.SecondClass
type=Map
-> InnerException:
Error while compiling
source=System.Nullable`1[Model.IdentityType]
destination=Model.KeyValueData
type=Map
--> InnerException:
No default constructor for type 'KeyValueData', please use 'ConstructUsing' or 'MapWith'

[WahidBitar]

I've figured a way out but still think it might be a better if we've somthing more helpful in the config. Especially from primitive types to classes. Anyways, my solution was simply like the following:

config.NewConfig(typeof(Nullable<>), typeof(KeyValueData))
            .IgnoreNullValues(true)
            .Map("key", "Value")
            .MapToConstructor(true);

[DocSvartz]

Hello @WahidBitar , if your goal is to skipped mapping when the TSource is null, maybe your help .IgnorIf()

[DocSvartz]

Hello @WahidBitar, I ran into this problem while preparing a fix for the problem record detection.

Please add sample Type of KeyValueData. To make it easier to understand which way the processing is going

[WahidBitar]

Thanks @DocSvartz , My main goal is not to skip the null values. My goal is to map from a nullable enum to my custom class KeyValueData in a general way.
I'll put here the entire aspects and my work around so you may take benifit of it.

Note: you may found something weard in my KeyValueData class because I have a general mapper from Enum to string because I put translation of the enums in the Resources files, so If you don't have this case your config should be simpler. Anyway here is my classes and config:

Mapping config:

public class GeneralMapper : IRegister
{
    public void Register(TypeAdapterConfig config)
    {
        // by default the following config will cause the Key property in the KeyValueData to get the value from the resources.
        // so I've updated the KeyValueData class to ignore the setter
        config.ForType<Enum, string?>()
            .MapWith(e => Enums.ResourceManager.GetString(e.ToResourceKey()) ?? e.ToString());
        
        config.NewConfig<Enum, KeyValueData?>()
            .MapWith(s => new KeyValueData(s));
        
        config.NewConfig(typeof(Nullable<>), typeof(KeyValueData))
            .MapToConstructor(true)
            .Map("key", "Value");
    }
}

the KeyValueData class:

public record KeyValueData
{
    private readonly string? keyHolder; // I had to set this field to this name becuase key will get the value from Resources
    private string? description;

    public KeyValueData(Enum key)
    {
        this.keyHolder = key.ToString();
        Description = Enums.ResourceManager.GetString(key.ToResourceKey()) ?? key.ToResourceKey();
    }

    public string Key
    {
        get => keyHolder!;
        set { } // Don't know why mapster call the setter after calling the constructor. I guess there is a bug related to this.
    }

    public string? Description
    {
        get => description;
        set => description ??= value;
    }
}

[DocSvartz]

@WahidBitar, I wanted to see the KeyValueData in order to better help you.
But yes, it won't solve your main problem (
Now I see next:

1. In this moment you Type KeyValueData has been detect Mapster as Class not as Record.
2. Activate Setter from Property Key possible linked from this bug in Class adapter I described it from this issue Mapster.tool MapToConstructor reassigns a object property despite assigning it in the constructor  #633.

You use Record only as immutable type ? Or you used in this time mutable behavior from update.

Example:

_destination = new KeyValueData();
var result = _Input.adapt(_desination)
var checkresult = object.ReferenceEquals(_result, _desination) //  return true. _result is not modified copy _destination.

[DocSvartz]

Hello @WahidBitar , In version Mapster 7.4.0 and Mapster Tool 8.4.0 (Net 7.0) it working

from your last example: not Error

 public class GeneralMapper : IRegister
 {
     public void Register(TypeAdapterConfig config)
     {
         config.NewConfig<Enum?, KeyValueData?>()
         .MapWith(s => s == null ? null : new KeyValueData(s));
     }
}

Result of generation:

public partial class FooMapper : TEstConsole.Mapster.IFooMapper
{
    public TEstConsole.clases.KeyValueData MapToEntity(System.Enum s)
    {
        return s == null ? null : new TEstConsole.clases.KeyValueData(s);
    }
}

[WahidBitar]

thank you so much @DocSvartz
till now I don't use the Mapster Tool, but I am using the Mapster 7.4.0 and don't know why this config didn't work for me

config.NewConfig<Enum?, KeyValueData?>()
            .MapWith(s => s == null ? null : new KeyValueData(s.ToString(), Enums.ResourceManager));

so I ended up with my workaround solution

[DocSvartz]

I get you Error Result. Try found problem :)

[DocSvartz]

@WahidBitar @andrerav

Looks like I made a fix from this problem.

@andrerav i can integrated this fix from my PR #634 or is it better to open a new PR?

Upd:
I'll open a new PR, I got a solution, but I don't like it :). Perhaps someone can improve it.

[andrerav]

@DocSvartz Yes I prefer a separate PR :) Thanks for all your recent contributions, amazing work!

[stagep]

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