I'll begin 2023 (late February :)) posts with a quick puzzle about C#.
Given the program below answer the following questions:
1. What is its output ?
2. Can you spot/explain the issues in the code?
3. How could one pinpoint the issue?
Of course you are free to compile/run it, and I do encourage you to do so, but I do suggest to only do it after you have formulated an hypothesis or if only inspecting the code does not ring any bells.
See you in the next post.
Have fun!
Adriano
Je commencerai les messages de 2023 (fin février :)) avec une petite casse-tête sur C#.
Compte tenu du programme ci-dessous, répondez aux questions suivantes:
1. Quelle est sa sortie ?
2. Pouvez-vous repérer/expliquer les problèmes dans le code ?
3. Comment identifier le problème ?
Bien sûr, vous êtes libre de le compiler/l'exécuter, et je vous encourage à le faire, mais je suggère de ne le faire qu'après avoir formulé une hypothèse ou si seulement inspecter le code ne vous dit rien.
A bientôt
Amusez-vous!
Adriano
Vou começar os posts de 2023 (no final de Fevereiro :)) com um pequeno quebra-cabeças em C#.
Dado o programa abaixo, responda as seguintes questões:
1. O que será impresso?
2. Você é capaz de apontar/explicar os problemas no mesmo?
3. Como poderíamos notar o problema apenas fazendo inspeção do código?
Claro que você pode compilar/rodar o programa (inclusive eu recomendo que você o faça), contudo seria interessante criar uma hipotese antes.
Até o próximo post.
Divirta se!
Adriano
class User
{
public string Name;
public User Manager;
public IList Addresses;
public User(string name, User manager)
{
Name = name;
Manager = manager;
}
}
class Address
{
public string Street;
public Address(string street)
{
Street = street;
}
}
using (var db = Db4oEmbedded.OpenFile(databaseFileName))
{
List<Address> addrs = new List();
addrs.Add(new Address("Street1"));
addrs.Add(new Address("Street2"));
User fooManager = new User("Foo") { Addresses = addrs };
User fooBarManager = new User("FooBar", fooManager);
User barManager = new User("John Doe", fooBarManager);
User user = new User("Adriano", barManager);
db.Store(user);
}
using (var db = Db4oEmbedded.OpenFile(databaseFileName))
{
var query = db.Query();
query.Constrain(typeof (User));
query.Descend("Name").Constrain("Adriano");
User user = (User) query.Execute()[0];
Console.WriteLine(user.Manager.Manager.Manager.Addresses[0].Street);
}
using Db4objects.Db4o;
using Db4objects.Db4o.Linq;
using System.Linq;
class Item
{
public string Name { get; set; }
public Item Father { get; set ; }
}
public class Test
{
private const string DatabaseFile = "wwwtc1.odb";
private static void Main()
{
Item item1 = new Item { Name = "Adriano" };
using (var db = Db4oEmbedded.OpenFile(DatabaseFile))
{
db.Store(item1);
}
using (var db = Db4oEmbedded.OpenFile(DatabaseFile))
{
Item item2 = new Item {Name = "Carol", Father = item1 };
db.Store(item2);
}
}
}
If you have done some work with db4o you probably will easily spot the problem.