.net - 如何注册通用对象工厂？

Question

我有以下两个类(class):

public class KeyedEntity<TEntity>
{
    internal KeyedEntity() { }

    public Identifier Key { get; set; }
    public TEntity Entity { get; set; }
}

public static class KeyedEntity
{
    public static KeyedEntity<TEntity> Create<TEntity>(Identifier key, TEntity entity)
    {
        return new KeyedEntity<TEntity>
        {
            Key = key,
            Entity = entity,
        };
    }
}

构造函数的原因是internal第二类存在是我想强制执行更具高度可维护性的 KeyedEntity.Create(x, y)语法而不是 new KeyedEntity<T>{ Key = x, Entity = y } 。 (请注意，类型是使用以前的语法推断的。)

我想告诉 AutoFixture 如何创建 KeyedEntity 的实例。然而，Register方法似乎只允许注册单一类型而不是开放的泛型类型。

如何注册KeyedEntity.Create<TEntity>作为 KeyedEntity<TEntity> 的创建函数？

Answer 1

为了支持您的开放通用类型，您可以编写自定义样本生成器:

public class KeyedEntityBuilder : ISpecimenBuilder
{
    private readonly static MethodInfo createMethod =
        typeof(KeyedEntity).GetMethod("Create");

    public object Create(object request, ISpecimenContext context)
    {
        var t = request as Type;
        if (t == null ||
            !t.IsGenericType ||
            t.GetGenericTypeDefinition() != typeof(KeyedEntity<>))
            return new NoSpecimen(request);

        var entityType = t.GetGenericArguments().Single();

        var key = context.Resolve(typeof(Identifier));
        var entity = context.Resolve(entityType);

        return createMethod
            .MakeGenericMethod(entityType)
            .Invoke(null, new[] { key, entity });
    }
}

(为了清楚起见，省略了防御性编码。)

以下单元测试通过:

public class Tests
{
    [Fact]
    public void CreateKeyedEntity()
    {
        var fixture = new Fixture();
        fixture.ResidueCollectors.Add(new KeyedEntityBuilder());

        var actual = fixture.Create<KeyedEntity<Foo>>();

        Assert.NotNull(actual.Key);
        Assert.NotNull(actual.Entity);
    }
}

为了更好的可维护性，您应该封装 KeyedEntityBuilder in a Customization .