Great, all works now, thanks! 
See ya!
P.D: Errr… i think i hit another problem with pointers :S.
I changed my TMap this way:
class ProviderCatalogs : public TMap < FString, UDataTable* > {};
...]
ProviderCatalogs* catalogs;
I’m using pointers because i need that this “catalogs” variable be modified by my DirectoryVisitor class.
All was working fine, until i tried this:
UDataTable* providerArticles = catalogs[provider];
and i got this error:
Error 1 error C2677: ‘’ binario : no se encontró un operador global que adopte el tipo ‘FString’ (o bien no existe una conversión aceptable) M:\Documentos\Copy\Programacion\Proyectos\UE4\MyShop\Source\MyShop\Providers.cpp 119 1 MyShop
I don’t know what i’m doing wrong. I created a pointer to a ProviderCatalogs object, that is really a TMap<FString, UDataTable*>, so, i should be able to access a value with a string key, right? 
.
See ya!
P.D 2: I forgot to specify that “provider” is a FString, this is the function at the moment:
void AProviders::GetArticle(FString provider, FString articleCode)
{
if (catalogs->Num() > 0)
{
if (catalogs->Contains(provider))
{
**UDataTable* providerArticles = catalogs[provider];**
//providerArticles->FindRow(articleCode, TEXT("Searching article"));
}
}
}