使用 C# 结构体在域模型中循环引用

发布于 2024-11-18 16:02:59 字数 270 浏览 8 评论 0原文

当两个结构之间存在循环引用时会发生什么？对于下面的示例，内存分配是如何工作的，或者会产生错误吗？

    public struct MultipleChoiceQuestion
    {
        public IEnumerable<Option> Options;
    }

    public struct Option
    {
        public MultipleChoiceQuestion Question;
    }

原文

What happens when there is a circular reference between two structs? How does memory allocation work for the example below or would it yield and error?

    public struct MultipleChoiceQuestion
    {
        public IEnumerable<Option> Options;
    }

    public struct Option
    {
        public MultipleChoiceQuestion Question;
    }

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扮仙女 2024-11-25 16:02:59

MultipleChoiceQuestion 中的 Options 字段只是一个参考，默认情况下为 null。 Option 中的 Question 字段是一个 MultipleChoiceQuestion 类型的值，默认情况下将具有默认值。这里没有问题（除了在多种方面存在问题的设计之外）。

导致逻辑内存问题的真正循环引用将无法编译：

struct Foo
{
    Bar bar;
}

struct Bar
{
    Foo foo;
}

Test.cs(6,9)：错误CS0523：“Bar”类型的结构成员“Foo.bar”导致结构布局中出现循环
Test.cs（11,9）：错误CS0523：“Foo”类型的结构成员“Bar.foo”导致结构布局中出现循环

The Options field in MultipleChoiceQuestion is just a reference here, which will be null by default. The Question field in Option is a value of type MultipleChoiceQuestion which will have its default value by default. There's no problem here (other than a questionable design in more ways than one).

A genuine circular reference leading to a logical memory problem will fail to compile:

struct Foo
{
    Bar bar;
}

struct Bar
{
    Foo foo;
}

Test.cs(6,9): error CS0523: Struct member 'Foo.bar' of type 'Bar' causes a cycle in the struct layout
Test.cs(11,9): error CS0523: Struct member 'Bar.foo' of type 'Foo' causes a cycle in the struct layout

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此刻的回忆 2024-11-25 16:02:59

问题（属性）是封装；问题是外部结构的一部分，通过字段。

然而，选项是对产生一个或多个选项的外部对象的引用；每次都会复制这些内容。

这里还有其他几个错误：

可变结构：EVIL
公共字段：EVIL
选项作为列表会更好；并非所有枚举都是可重复的，
它们不是“值” - 所以它们不应该是结构体；在我看来，使用类来代替

：

public class MultipleChoiceQuestion
{
    private readonly List<Option> options
        = new List<Option>();
    public IList<Option> Options {get { return options; } }
}

public class Option
{
    public MultipleChoiceQuestion Question {get;set;}
}

Question (property) is encapsulation; the question is part of the outer struct, via a field.

Options, however, is a reference to an external object that yields one or more Options; these will be copied each time.

There are several other mistakes here:

mutable structs: EVIL
public fields: EVIL
the Options would be better as a list; not all enumerables are repeatable
they aren't "values" - so they should not be structs; use classes instead

IMO:

public class MultipleChoiceQuestion
{
    private readonly List<Option> options
        = new List<Option>();
    public IList<Option> Options {get { return options; } }
}

public class Option
{
    public MultipleChoiceQuestion Question {get;set;}
}

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