在 C++ 中导致编译错误的结构 Class

Question

我在编译 C++ class 时遇到错误，它与要从方法返回的结构有关。我已将代码条带化到最低限度，但仍然出现错误。我正在使用 Visual Studio 6.0.

代码

// TestClass.cpp: implementation of the TestClass class.
//
//////////////////////////////////////////////////////////////////////

#include "stdafx.h"
#include "TestClass.h"

//////////////////////////////////////////////////////////////////////
// Construction/Destruction
//////////////////////////////////////////////////////////////////////

TestClass::TestClass()
{

}

TestClass::~TestClass()
{

}

ProductInfo TestClass::GetProdInfo()
{
    ProductInfo PI;

    return PI;
}

// TestClass.h: interface for the TestClass class.
//
//////////////////////////////////////////////////////////////////////

#if !defined(AFX_TestClass_H__081E411D_44F9_4E0B_9FE7_CF6F708BE769__INCLUDED_)
#define AFX_TestClass_H__081E411D_44F9_4E0B_9FE7_CF6F708BE769__INCLUDED_

#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000

class TestClass  
{
public:
    struct ProductInfo
    {
        char    cCode;
        char    cItem[20];
        long    lValue;
    };

public:
    TestClass();
    virtual ~TestClass();

private:
    ProductInfo GetProdInfo();
};

#endif // !defined(AFX_TestClass_H__081E411D_44F9_4E0B_9FE7_CF6F708BE769__INCLUDED_)

收到错误

Compiling...
TestClass.cpp
C:\Work\TestStruct\TestClass.cpp(22) : error C2143: syntax error : missing ';' before 'tag::id'
C:\Work\TestStruct\TestClass.cpp(22) : error C2501: 'ProductInfo' : missing storage-class or type specifiers
C:\Work\TestStruct\TestClass.cpp(22) : fatal error C1004: unexpected end of file found
Error executing cl.exe.

TestStruct.exe - 3 error(s), 0 warning(s)

知道我为什么会收到这些错误吗？

谢谢

Answer 1

ProductInfo 是 TestClass 中的嵌套 class，因此您必须在此处保留命名空间。

TestClass::ProductInfo TestClass::GetProdInfo()

标准说：

9.7 Nested class declarations

If class X is defined in a namespace scope, a nested class Y may be declared in class X and later defined in the definition of class X or be later defined in a namespace scope enclosing the definition of class X.

7.3.1 Namespace definition

The enclosing namespaces of a declaration are those namespaces in which the declaration lexically appears, except for a redeclaration of a namespace member outside its original namespace (e.g., a definition as specified in 7.3.1.2). Such a redeclaration has the same enclosing namespaces as the original declaration.

Answer 2

您必须取消嵌套结构或更改 GetProdInfo

的 return 类型

TestClass::ProductInfo TestClass::GetProdInfo()
{
    ProductInfo PI;

    return PI;
}

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