如何正确实现 IUserType?

问题描述

我需要创建一个 自定义类型用于NHibernate，通过编写一个实现了IUserType的新映射器类.虽然覆盖大多数方法和属性相对简单，但我在理解如何正确处理以下成员时遇到了一些困难:

I need to create a custom type for NHibernate by writing a new mapper class that implements IUserType. While it is relatively straightforward to override most of the methods and properties, I get some difficulties to understand how to deal correctly with the following members:

• object Assemble(object cached, object owner);
• object DeepCopy(object value);
• object Disassemble(object value);
• object Replace(object original, object target, object owner);

我不明白他们的目的到底是什么；更重要的是，如何正确实施它们.我见过的大多数示例都只返回原始输入参数.

I do not understand what is exactly their purpose; and more important, how to properly implement them. Most of the examples I have seen just return the raw input parameter.

public object DeepCopy(object value)
{
    return value;
}

public object Replace(object original, object target, object owner)
{
    return original;
}

public object Assemble(object cached, object owner)
{
    return cached;
}

public object Disassemble(object value)
{
    return value;
}

如何在真实案例或更复杂的场景中正确实现这些方法?

推荐答案

看看 Ritesh Rao 如何在他的 NCommon 框架:

Have a look at how Ritesh Rao has done this in his NCommon framework:

MoneyUserType 实现了一个名为 CompositeUserTypeBase

评论中有更多细节，但要总结一下:

There's more detail in the comments but to summarize:

• DeepCopy - 应该返回持久状态的深层副本，在实体和集合处停止
• 反汇编 - 将对象转换为其可缓存"表示(即关联必须作为标识符值缓存)
• 组装 - 从可缓存的表示中重建一个对象

这里有更详细的解释

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