Mapping nullable Enum to custom object

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'

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);

@WahidBitar

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

@WahidBitar

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

@DocSvartz

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;
    }
}

@WahidBitar

@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:

In this moment you Type KeyValueData has been detect Mapster as Class not as Record.
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.

@WahidBitar

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);
    }
}

@DocSvartz

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

I get you Error Result. Try found problem :)

@WahidBitar

@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.

@DocSvartz

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

Fix Issue MapsterMapper#640

Merge pull request #643 from DocSvartz/NullableEmuninParamFix

In order to identify issues that are still active, we are closing issues that we believe are either resolved or are dormant. If your issue is still active then please reopen. Thanks.

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Mapping nullable Enum to custom object #640

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WahidBitar commented on Oct 8, 2023

DocSvartz commented on Oct 8, 2023

DocSvartz commented on Oct 9, 2023

WahidBitar commented on Oct 9, 2023

DocSvartz commented on Oct 9, 2023

DocSvartz commented on Oct 10, 2023

WahidBitar commented on Oct 10, 2023

DocSvartz commented on Oct 10, 2023

DocSvartz commented on Oct 13, 2023

andrerav commented on Oct 15, 2023

stagep commented on Jan 7, 2025

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