C#从方法返回结构引用 [英] C# return struct reference from method

问题描述

在 C++ 中，返回在方法中分配在堆栈上的对象的引用会产生垃圾值，因为一旦方法离开作用域，堆栈对象就会被销毁.鉴于在 C# 中结构是在堆栈上分配的，这也会产生垃圾值吗?

In C++, returning a reference of an object allocated on the stack in a method, yields garbage values due to the fact, that the stack object is destroyed as soon the method leaves the scope. Given that in C# structs are allocated on the stack, would this yield garbage values as well?

struct Test
{
    //data
}

Test Foo()
{
    Test t1 = new Test();
    return t1;
}

推荐答案

我认为您应该阅读以下内容:http://mustoverride.com/ref-returns-and-locals/

I think you should read this: http://mustoverride.com/ref-returns-and-locals/

简而言之，C# 设计团队决定禁止通过引用返回局部变量.

In short, the C# Design team decided to disallow returning local variables by reference.

– 禁止通过引用返回局部变量.这是为 C# 选择的解决方案.- 保证引用确实不超过引用的变量 C# 不允许返回通过引用引用局部变量.有趣的是，这是Rust 使用的相同方法，尽管原因略有不同.(Rust 是一种 RAII 语言，退出时会主动销毁本地人范围)

– Disallow returning local variables by reference. This is the solution that was chosen for C#. - To guarantee that a reference does not outlive the referenced variable C# does not allow returning references to local variables by reference. Interestingly, this is the same approach used by Rust, although for slightly different reasons. (Rust is a RAII language and actively destroys locals when exiting scopes)

即使使用 ref 关键字，如果您继续尝试:

Even with the ref keyword, if you go ahead and try this:

public struct Test
{
    public int a;
}

public ref Test GetValueByRef()
{
    var test = new Test();
    return ref test;
}

您将看到编译器出现以下错误:

You will see that the compiler errors out with the following:

不能通过引用返回本地test"，因为它不是本地引用

Cannot return local 'test' by reference because it is not a ref local

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