C++ 中的 toString() 方法？

Question

不确定我做错了什么，但我的代码是这样的：

std::wstring MediaDescription::toString()
{
    std::wstring theFile = std::wstring(L"\"fileName\":\"") + mFilename + std::wstring(L"\"");
    std::wstring theAuthor = std::wstring(L"\"author\":\"") + mAuthor + std::wstring(L"\"");
    std::wstring theAlbum = std::wstring(L"\"album\":\"") + mAlbum + std::wstring(L"\"");
    std::wstring theGenre = std::wstring(L"\"genre\":\"") + mGenre + std::wstring(L"\"");
    std::wstring theType = std::wstring(L"\"mediaType\":") + mMediaType;
    std::wstring theTitle = std::wstring(L"\"title\":\"") + mTitle + std::wstring(L"\"");
    return std::wstring(L"{") + theFile + std::wstring(L",") + theAuthor + std::wstring(L",") + theAlbum + std::wstring(L",") + theGenre + std::wstring(L",") + theType + std::wstring(L",") + theTitle +     std::wstring(L"}");
}

我得到的错误是：

 class:"MediaDescription" has no member of "toString"

但我不明白如何正确修改语法或缺少什么。这是试图将 toString 从 Java 转换为 C++ 语法。

我的头文件如下：

#pragma once

#include <iostream>
#include <memory>
#include <string>

class MediaDescription : public std::enable_shared_from_this<MediaDescription>
{

/// <summary>
/// A media type of either Music or Video.
/// </summary>
private:
const std::wstring mMediaType;
/// <summary>
/// A title of a song or a video/movie.
/// </summary>
const std::wstring mTitle;
/// <summary>
/// A name for the author/actor/actress of the media.
/// </summary>
const std::wstring mAuthor;
/// <summary>
/// A name for the album of the song.
/// </summary>
const std::wstring mAlbum;
/// <summary>
/// A genre of the video.
/// </summary>
const std::wstring mGenre;
/// <summary>
/// A filename of the media
/// </summary>
const std::wstring mFilename;

public:
MediaDescription();

/// <summary>
/// MediaDescription constructor. </summary>
/// <param name="mediaType"> a media type of music or video </param>
/// <param name="title"> the title of the media </param>
/// <param name="author"> the author of the media </param>
/// <param name="album"> the album only applying to music </param>
/// <param name="genre"> the genre of the media </param>
/// <param name="filename"> the filename of the media </param>
MediaDescription(const std::wstring &mediaType, const std::wstring &title, const std::wstring &author, const std::wstring &album, const std::wstring &genre, const std::wstring &filename);

/// <summary>
/// Returns a media type of either music or video. </summary>
/// <returns> a media type. </returns>
virtual std::wstring getMediaType();

/// <summary>
/// Returns a title of a song or video/movie.
/// </summary>
/// <returns> a title of the media. </returns>
virtual std::wstring getTitle();

/// <summary>
/// Returns a name for the author of the media or leading actor/actress of video.
/// </summary>
/// <returns> a name of the author/actor/actress </returns>
virtual std::wstring getAuthor();

/// <summary>
/// Returns a name for the album of the song.
/// </summary>
/// <returns> a name of the album. </returns>
virtual std::wstring getAlbum();   

/// <summary>
/// Returns a genre of the video/movie.
/// </summary>
/// <returns> a genre of the video. </returns>
virtual std::wstring getGenre();

/// <summary>
/// Returns a filename of the media file.
/// </summary>
/// <returns> a filename of the media. </returns>
virtual std::wstring getFilename();
};

如果我这样做：

virtual std::wstring toString() override;

然后我得到以下错误：

'MediaDescription::toString': method with override specifier 'override' did not override any base class methods

Answer 1

您可能应该像这样修改名为 MediaDescription 的 class：

class MediaDescription {
/*code*/
public: /*or anything you need*/
    /*code*/
    std::wstring toString();
}

Answer 2

另一种选择是添加对 std::to_string 的覆盖：

#include <string>
std::string std::to_string(MediaDescription &value) {
    // convert to string ...
}

This 也是一个选项。

Answer 3

如果您在子 class 的虚函数上指定 override C++11 关键字，其父 class 必须具有相同的虚函数签名。

Live example

#include <iostream>
using namespace std;

struct Parent
{
    virtual void DoWork1() {}
    void DoWork2() {}
};

struct Child : Parent
{
    void DoWork1() override {} // OK !
    void DoWork1(int) override {} // error !

    void DoWork2() override {} // error !
};

int main()
{
}

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