我如何注册一个通用的对象工厂？ [英] How can I register a generic object factory?

问题描述

我有以下两类：

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,
        };
    }
}

究其原因，构造函数是内部第二类存在是我要执行更多的高维护 KeyedEntity.Create（X，Y ）语法，而不是新KeyedEntity＆LT; T＆GT; {键= X，实体= Y} 。 （请注意，类型推断与前者的语法。）

The reason the constructor is internal and the second class exists is I want to enforce the more highly-maintainable KeyedEntity.Create(x, y) syntax rather than new KeyedEntity<T>{ Key = x, Entity = y }. (Note that the type is inferred with the former syntax.)

我想告诉AutoFixture如何创建 KeyedEntity 的实例。但是，注册办法似乎只能允许一个单一类型的注册，而不是开放式泛型类型。

I want to tell AutoFixture how to create an instance of KeyedEntity. However, the Register method only seems to allow registration of a single type rather than an open generic type.

如何注册 KeyedEntity.Create＆LT; TEntity＆GT; 作为创建函数 KeyedEntity＆LT; TEntity＆GT;

How can I register KeyedEntity.Create<TEntity> as the creation function for KeyedEntity<TEntity>?

推荐答案

要支持你的开放式泛型类型，你可以写一个自定义的样本生成器的：

To support your open generic type, you can write a custom Specimen Builder:

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 });
    }
}

（防御编码省略清晰。）

(Defensive coding omitted for clarity.)

下面的单元测试通过：

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，你应该封装 KeyedEntityBuilder 在自定义。

For better maintainability, you should encapsulate KeyedEntityBuilder in a Customization.

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