How to avoid creating a new instance of object using "Deep destination property" feature

[plenartowicz]

Hi,
I have a question about "Deep destination property" feature:

There is a code from a wiki page: https://github.com/MapsterMapper/Mapster/wiki/Custom-mapping#deep-destination-property

TypeAdapterConfig<Poco, Dto>.NewConfig()
    .Map(dest => dest.Child.Name, src => src.Name);

Is there any way to avoid creating instance of the Child object if src.Name is null?
Or even better, if I write something like this:

TypeAdapterConfig<Poco, Dto>.NewConfig()
    .Map(dest => dest.Child.Name, src => src.Name, src => src.Name == "Peter");

Now, I always get empty instance of the Child object and dest.Child.Name == null even if the condition return false.

[DocSvartz]

Hi @plenartowicz , I think something like this:

[TestMethod]
public void TestFindObject()
{

    TypeAdapterConfig<People901, People902>
         .NewConfig()
         .Map(dest => dest.Child.Name, src => src.Name)
         .IgnoreIf((src, dest) => !NameHelper.CheckNames(src.Name), dest => dest.Child);


    var source = new People901() { Name = "Mike"};

    var resultforMike = source.Adapt<People902>(); // dest.Child == null


    var resultforMary = new People901() { Name = "Mary" }
        .Adapt<People902>(); //dest.Child is not null Child.Name == "Mary"


}

public static class NameHelper
{
     public static bool CheckNames(string name)
    {
        if (String.IsNullOrEmpty(name))
            return false;


        var list = new List<String>()
        {
            "Mary",
            "John",
            "Robert"

        };

        return list.Contains(name);
    }
}

public class People901
{
    public string Name { get; set; }

}

public class People902
{
    public string Name { get; set; }

    public People902 Child { get; set; }
}

[plenartowicz]

It's working, thanks a lot 😄

But still I'm a little bit confused why it does not work.

TypeAdapterConfig<Poco, Dto>.NewConfig()
    .Map(dest => dest.Child.Name, src => src.Name, src => src.Name == "Peter");

IMO, if shouldMap returns false then whole destination path should be ignored, not only the last part.

Maybe it is a bug? 🤔

[DocSvartz]

I don't know exactly what the original author intended, but I think the name "Deep destination property" accurately reflects what's going on.

You're asking to map the source property Name to the destination property Name using deep destination path dest.Child

It follows that if the condition src.Name == "Peter" is triggered and Child is absent in the source, the value Name will be transferred to destination Child == null , which is not possible 😂

Upd:

It's noted here that this doesn't stop mapping.
And given the above, dest.Child must exist in any case.

[plenartowicz]

I see now, thanks 👍