Unique_Ptr: 正在尝试引用已删除的函数
Unique_Ptr: Attemting To Reference A Deleted Function
所以我现在正在用 C++ 做一个学校项目，尽管我还不太熟悉这种语言。
整个项目分为几个里程碑。
1：读取包含不同类型生物的列表并将它们存储在向量中
2：读取一个TGA-File，存入一个class。
...
5: 每次读取 Creature-Type 读取一个 TGA-Picture 并将其存储以备后用。 （在 GUI 上打印，Remove/add）
所以我认为将每种类型的图片存储在 class 本身中是个好主意，因为它应该只加载一次。
我的 TGAPicture class 中的 load() 函数将 return std::unique_ptr 所以我在我的 CreatureType class 中添加了类型作为参数。
这样做之后，我得到了几个这样的错误：
Error C2280 'biosim::CreatureType::CreatureType(const biosim::CreatureType &)': attempting to reference a deleted function bio-sim-qt E:\Development\C++\bio-sim-qt\bio-sim-qt\qtmain.cpp 58 1
Error (active) function "biosim::CreatureType::CreatureType(const biosim::CreatureType &)" (declared implicitly) cannot be referenced -- it is a deleted function bio-sim-qt e:\Development\C++\bio-sim-qt\bio-sim-qt\Model.cpp 15 26
所以我阅读了大约 10 个标题与我相似的问题，每个问题都指出，你不能复制 unique_ptr 并建议解决方案，例如使用 std::move() 或 returning一个参考。
虽然我尝试使用这些来解决我的问题，但我一点也做不到，可能是因为我是 C++ 的新手并且从未使用过唯一指针。
这是代码，似乎与我相关：
/**
* @class CreatureType
* Object of the various CreatureTypes ingame
*/
class CreatureType {
private:
std::string name;
int strengh;
int speed;
int lifespan;
std::vector<std::string> attributes;
std::string path;
std::unique_ptr<TGAPicture> picture; //What I tried to add in order to stre my pictures
public:
CreatureType(const std::string& name
, int strengh, int speed, int lifespan
, const std::vector<std::string>& basic_strings
, const std::string& path);
/**
* Initializes list with CreatureTypes by reading from a .txt-File
*/
static CreatureList load(const std::string& file);
/**
* Printing Data in various ways
*/
void getInfo() const;
void getInfoInOneLine() const;
std::string getName() const;
int getStrengh() const;
int getSpeed() const;
int getLifespan() const;
std::vector<std::string> getAttributes() const;
std::string getPath() const;
};
}
CreatureType::CreatureType(const std::string& name
, int strengh, int speed, int lifespan
, const std::vector<std::string>& basic_strings
, const std::string& path)
: name(name),
strengh(strengh),
speed(speed),
lifespan(lifespan),
attributes(basic_strings),
path(path),
picture(TGAPicture::loadPicture(Reference::PicturePath::creatureBasePath + path)){ }
/**
* Implementation Notes:
* - Does a line not fullfill the requirenments, it will be ignored
* - @see <a href="https://elearning.uni-bayreuth.de/pluginfile.php/644828/mod_resource/content/2/Aufgabenblatt_1.pdf">Formation</a>
* - Prints data with std::cout
*/
CreatureList CreatureType::load(const std::string& file) {
CreatureList creatureList;
std::ifstream fileStream; //Datei-Handle
int lineNumber = 0;
int correctLinesRead = 0;
fileStream.open(file, std::ios::in);
if (!fileStream.is_open()) {
throw FileNotFoundException(file);
}
logger << INFO << "Einlesevorgang wird gestartet\n";
//One line per loop
while (!fileStream.eof()) {
bool skipLine = false;
std::string line;
getline(fileStream, line);
lineNumber++;
... //Checking if data is valid
//Every Parameter does exist and is valid
creatureList.push_back(CreatureType(creatureArgs[0]
, strengh, speed, lifespan
, attributes, creatureArgs[5]));
correctLinesRead++;
}
return creatureList;
}
TGA图片：
//no padding bytes
#pragma pack( push, 1 )
/**
* @struct TGAHeader
* Represents the standard TGA-Header.
*/
struct TGAHeader {
char idLength;
char colourmapType;
char imagetype;
short colourmapStart;
short colourmapLength;
char colourmapBits;
short xOrigin;
short yOrigin;
short width;
short height;
char bits;
char descriptor;
};
#pragma pack( pop )
/**
* @struct RGBA
* Represents a Pixel with a red, green, blue and possibly alpha value
*/
struct RGBA {
std::uint8_t B, G, R, A;
};
/**
* @class TGAPicture
* Class used to represent TGA-Files, that are used in the program
*/
class TGAPicture {
public:
TGAPicture(const TGAPicture& other)
: pixel(other.pixel),
header(other.header),
width(other.width),
height(other.height),
size(other.size),
bitsPerPixel(other.bitsPerPixel) {}
TGAPicture(TGAPicture&& other) noexcept
: pixel(std::move(other.pixel)),
header(std::move(other.header)),
width(other.width),
height(other.height),
size(other.size),
bitsPerPixel(other.bitsPerPixel) {}
TGAPicture& operator=(const TGAPicture& other) {
if (this == &other)
return *this;
pixel = other.pixel;
header = other.header;
width = other.width;
height = other.height;
size = other.size;
bitsPerPixel = other.bitsPerPixel;
return *this;
}
TGAPicture& operator=(TGAPicture&& other) noexcept {
if (this == &other)
return *this;
pixel = std::move(other.pixel);
header = std::move(other.header);
width = other.width;
height = other.height;
size = other.size;
bitsPerPixel = other.bitsPerPixel;
return *this;
}
private:
std::vector<RGBA> pixel; //Containes every pixel of the picture
TGAHeader header;
short width, height, size, bitsPerPixel;
...
public:
/**
* Loads and initializes a picture to be used in the program
* @throws TGAExpection if file could not be loaded
*/
static std::unique_ptr<TGAPicture> loadPicture(const std::string& path);
TGAPicture(const std::vector<RGBA>& pixel, const TGAHeader& header);
~TGAPicture();
....
};
}
#endif
cpp:
TGAPicture::TGAPicture(const std::vector<RGBA>& pixel, const TGAHeader& header)
: pixel(pixel),
header(header),
width(header.width),
height(header.height),
size(header.width * header.height * (header.bits / 8)),
bitsPerPixel(header.bits) { }
std::unique_ptr<TGAPicture> TGAPicture::loadPicture(const std::string& path) {
...
for (int i = 0; i < header.height * header.width; i++) {
pixel[i].B = *(bufferPosition++);
pixel[i].G = *(bufferPosition++);
pixel[i].R = *(bufferPosition++);
pixel[i].A = (header.bits > 24 ? *(bufferPosition++) : 0xFF);
}
/**
* Return unique_ptr
* - ObjectFactory
* - Automatic Deletion
*/
return std::unique_ptr<TGAPicture>{new TGAPicture(pixel, header)};
}
还有一个 class 有错误的是：
class Model {
public:
explicit Model(const CreatureList& creatureList);
~Model();
Terrain* getTerrain() const;
CreatureList& getCreatureList();
private:
CreatureList creatureList;
Terrain* terrain;
};
Model::Model(const CreatureList& creatureList) : creatureList(creatureList),
terrain(new Terrain()) {
for (CreatureType ty : creatureList) { //line with errror
ty.getInfoInOneLine();
}
}
我需要更改什么才能使其正常工作？什么是最佳方式？很确定我应该使用 unique_ptr 作为 return 用于 TGA::load() 方法。
我希望你能看穿这个烂摊子，如果我的英语不完美，我想道歉，因为这不是我的第一语言。
std::unique_ptr 不可复制。如果你能复制它就不再是独一无二的了。
您在 Model 的构造函数中的循环中创建了 creatureList 中元素的 副本 ，但它们有一个不可复制的成员，并且所以默认情况下它们本身是不可复制的。如果您实际上不需要元素的副本，则应使用引用：
Model::Model(const CreatureList& creatureList)
: creatureList(creatureList),
terrain(new Terrain())
{
for (CreatureType& ty : creatureList) { // changed to reference instead
// Note: this is still working with
// parameter, not the object's
// member.
ty.getInfoInOneLine();
}
}
您实际上并未提供 CreatureList 的定义，但我怀疑它也不可复制。这意味着无法将 Model::Model 的参数复制到对象的成员中。您有两种选择来解决此问题：确保移动您的 CreatureList 或使其可复制。
std::unique_ptr是可移动的，这意味着CreatureType也是默认的，所以你可以这样做：
Model::Model(CreatureList creatureList) // Take by value now
: creatureList(std::move(creatureList)), // Move the parameter to the member
terrain(new Terrain())
{
for (CreatureType& ty : this->creatureList) { // Use this-> to access member
// instead of now moved-from
// parameter. You could also
// just change them to have
// different names.
ty.getInfoInOneLine();
}
}
这会更改 Model 的构造函数以按值获取其参数并将该值移动到对象的 creatureList 成员中。
如果有意义，您还可以通过添加一个显式复制构造函数来复制 CreatureType 可复制，该复制构造函数复制 picture:
指向的对象
CreatureType::CreatureType(const CreatureType& other)
: name(other.name),
strengh(other.strengh),
speed(other.speed),
lifespan(other.lifespan),
attributes(other.attributes),
path(other.path),
picture(new TGAPicture(*other.picture))
{
}
如果这样做，编译器将不再生成隐式移动构造函数，因此您需要自己定义它：
CreatureType::CreatureType(CreatureType&& other)
: name(std::move(other.name)),
strengh(other.strengh),
speed(other.speed),
lifespan(other.lifespan),
attributes(std::move(other.attributes)),
path(std::move(other.path)),
picture(std::move(other.picture))
{
}
虽然 TGAPicture::loadPicture 到 return 和 std::unique_ptr 似乎没有任何理由。如果您只是 return 该函数的值，您将避免所有这些问题：
TGAPicture TGAPicture::loadPicture(const std::string& path) {
// ...
return TGAPicture{pixel, header};
}
所以我现在正在用 C++ 做一个学校项目，尽管我还不太熟悉这种语言。 整个项目分为几个里程碑。 1：读取包含不同类型生物的列表并将它们存储在向量中 2：读取一个TGA-File，存入一个class。 ... 5: 每次读取 Creature-Type 读取一个 TGA-Picture 并将其存储以备后用。 （在 GUI 上打印，Remove/add）
所以我认为将每种类型的图片存储在 class 本身中是个好主意，因为它应该只加载一次。 我的 TGAPicture class 中的 load() 函数将 return std::unique_ptr 所以我在我的 CreatureType class 中添加了类型作为参数。 这样做之后，我得到了几个这样的错误：
Error C2280 'biosim::CreatureType::CreatureType(const biosim::CreatureType &)': attempting to reference a deleted function bio-sim-qt E:\Development\C++\bio-sim-qt\bio-sim-qt\qtmain.cpp 58 1
Error (active) function "biosim::CreatureType::CreatureType(const biosim::CreatureType &)" (declared implicitly) cannot be referenced -- it is a deleted function bio-sim-qt e:\Development\C++\bio-sim-qt\bio-sim-qt\Model.cpp 15 26
所以我阅读了大约 10 个标题与我相似的问题，每个问题都指出，你不能复制 unique_ptr 并建议解决方案，例如使用 std::move() 或 returning一个参考。 虽然我尝试使用这些来解决我的问题，但我一点也做不到，可能是因为我是 C++ 的新手并且从未使用过唯一指针。
这是代码，似乎与我相关：
/**
* @class CreatureType
* Object of the various CreatureTypes ingame
*/
class CreatureType {
private:
std::string name;
int strengh;
int speed;
int lifespan;
std::vector<std::string> attributes;
std::string path;
std::unique_ptr<TGAPicture> picture; //What I tried to add in order to stre my pictures
public:
CreatureType(const std::string& name
, int strengh, int speed, int lifespan
, const std::vector<std::string>& basic_strings
, const std::string& path);
/**
* Initializes list with CreatureTypes by reading from a .txt-File
*/
static CreatureList load(const std::string& file);
/**
* Printing Data in various ways
*/
void getInfo() const;
void getInfoInOneLine() const;
std::string getName() const;
int getStrengh() const;
int getSpeed() const;
int getLifespan() const;
std::vector<std::string> getAttributes() const;
std::string getPath() const;
};
}
CreatureType::CreatureType(const std::string& name
, int strengh, int speed, int lifespan
, const std::vector<std::string>& basic_strings
, const std::string& path)
: name(name),
strengh(strengh),
speed(speed),
lifespan(lifespan),
attributes(basic_strings),
path(path),
picture(TGAPicture::loadPicture(Reference::PicturePath::creatureBasePath + path)){ }
/**
* Implementation Notes:
* - Does a line not fullfill the requirenments, it will be ignored
* - @see <a href="https://elearning.uni-bayreuth.de/pluginfile.php/644828/mod_resource/content/2/Aufgabenblatt_1.pdf">Formation</a>
* - Prints data with std::cout
*/
CreatureList CreatureType::load(const std::string& file) {
CreatureList creatureList;
std::ifstream fileStream; //Datei-Handle
int lineNumber = 0;
int correctLinesRead = 0;
fileStream.open(file, std::ios::in);
if (!fileStream.is_open()) {
throw FileNotFoundException(file);
}
logger << INFO << "Einlesevorgang wird gestartet\n";
//One line per loop
while (!fileStream.eof()) {
bool skipLine = false;
std::string line;
getline(fileStream, line);
lineNumber++;
... //Checking if data is valid
//Every Parameter does exist and is valid
creatureList.push_back(CreatureType(creatureArgs[0]
, strengh, speed, lifespan
, attributes, creatureArgs[5]));
correctLinesRead++;
}
return creatureList;
}
TGA图片：
//no padding bytes
#pragma pack( push, 1 )
/**
* @struct TGAHeader
* Represents the standard TGA-Header.
*/
struct TGAHeader {
char idLength;
char colourmapType;
char imagetype;
short colourmapStart;
short colourmapLength;
char colourmapBits;
short xOrigin;
short yOrigin;
short width;
short height;
char bits;
char descriptor;
};
#pragma pack( pop )
/**
* @struct RGBA
* Represents a Pixel with a red, green, blue and possibly alpha value
*/
struct RGBA {
std::uint8_t B, G, R, A;
};
/**
* @class TGAPicture
* Class used to represent TGA-Files, that are used in the program
*/
class TGAPicture {
public:
TGAPicture(const TGAPicture& other)
: pixel(other.pixel),
header(other.header),
width(other.width),
height(other.height),
size(other.size),
bitsPerPixel(other.bitsPerPixel) {}
TGAPicture(TGAPicture&& other) noexcept
: pixel(std::move(other.pixel)),
header(std::move(other.header)),
width(other.width),
height(other.height),
size(other.size),
bitsPerPixel(other.bitsPerPixel) {}
TGAPicture& operator=(const TGAPicture& other) {
if (this == &other)
return *this;
pixel = other.pixel;
header = other.header;
width = other.width;
height = other.height;
size = other.size;
bitsPerPixel = other.bitsPerPixel;
return *this;
}
TGAPicture& operator=(TGAPicture&& other) noexcept {
if (this == &other)
return *this;
pixel = std::move(other.pixel);
header = std::move(other.header);
width = other.width;
height = other.height;
size = other.size;
bitsPerPixel = other.bitsPerPixel;
return *this;
}
private:
std::vector<RGBA> pixel; //Containes every pixel of the picture
TGAHeader header;
short width, height, size, bitsPerPixel;
...
public:
/**
* Loads and initializes a picture to be used in the program
* @throws TGAExpection if file could not be loaded
*/
static std::unique_ptr<TGAPicture> loadPicture(const std::string& path);
TGAPicture(const std::vector<RGBA>& pixel, const TGAHeader& header);
~TGAPicture();
....
};
}
#endif
cpp:
TGAPicture::TGAPicture(const std::vector<RGBA>& pixel, const TGAHeader& header)
: pixel(pixel),
header(header),
width(header.width),
height(header.height),
size(header.width * header.height * (header.bits / 8)),
bitsPerPixel(header.bits) { }
std::unique_ptr<TGAPicture> TGAPicture::loadPicture(const std::string& path) {
...
for (int i = 0; i < header.height * header.width; i++) {
pixel[i].B = *(bufferPosition++);
pixel[i].G = *(bufferPosition++);
pixel[i].R = *(bufferPosition++);
pixel[i].A = (header.bits > 24 ? *(bufferPosition++) : 0xFF);
}
/**
* Return unique_ptr
* - ObjectFactory
* - Automatic Deletion
*/
return std::unique_ptr<TGAPicture>{new TGAPicture(pixel, header)};
}
还有一个 class 有错误的是：
class Model {
public:
explicit Model(const CreatureList& creatureList);
~Model();
Terrain* getTerrain() const;
CreatureList& getCreatureList();
private:
CreatureList creatureList;
Terrain* terrain;
};
Model::Model(const CreatureList& creatureList) : creatureList(creatureList),
terrain(new Terrain()) {
for (CreatureType ty : creatureList) { //line with errror
ty.getInfoInOneLine();
}
}
我需要更改什么才能使其正常工作？什么是最佳方式？很确定我应该使用 unique_ptr 作为 return 用于 TGA::load() 方法。 我希望你能看穿这个烂摊子，如果我的英语不完美，我想道歉，因为这不是我的第一语言。
std::unique_ptr 不可复制。如果你能复制它就不再是独一无二的了。
您在 Model 的构造函数中的循环中创建了 creatureList 中元素的 副本 ，但它们有一个不可复制的成员，并且所以默认情况下它们本身是不可复制的。如果您实际上不需要元素的副本，则应使用引用：
Model::Model(const CreatureList& creatureList)
: creatureList(creatureList),
terrain(new Terrain())
{
for (CreatureType& ty : creatureList) { // changed to reference instead
// Note: this is still working with
// parameter, not the object's
// member.
ty.getInfoInOneLine();
}
}
您实际上并未提供 CreatureList 的定义，但我怀疑它也不可复制。这意味着无法将 Model::Model 的参数复制到对象的成员中。您有两种选择来解决此问题：确保移动您的 CreatureList 或使其可复制。
std::unique_ptr是可移动的，这意味着CreatureType也是默认的，所以你可以这样做：
Model::Model(CreatureList creatureList) // Take by value now
: creatureList(std::move(creatureList)), // Move the parameter to the member
terrain(new Terrain())
{
for (CreatureType& ty : this->creatureList) { // Use this-> to access member
// instead of now moved-from
// parameter. You could also
// just change them to have
// different names.
ty.getInfoInOneLine();
}
}
这会更改 Model 的构造函数以按值获取其参数并将该值移动到对象的 creatureList 成员中。
如果有意义，您还可以通过添加一个显式复制构造函数来复制 CreatureType 可复制，该复制构造函数复制 picture:
CreatureType::CreatureType(const CreatureType& other)
: name(other.name),
strengh(other.strengh),
speed(other.speed),
lifespan(other.lifespan),
attributes(other.attributes),
path(other.path),
picture(new TGAPicture(*other.picture))
{
}
如果这样做，编译器将不再生成隐式移动构造函数，因此您需要自己定义它：
CreatureType::CreatureType(CreatureType&& other)
: name(std::move(other.name)),
strengh(other.strengh),
speed(other.speed),
lifespan(other.lifespan),
attributes(std::move(other.attributes)),
path(std::move(other.path)),
picture(std::move(other.picture))
{
}
虽然 TGAPicture::loadPicture 到 return 和 std::unique_ptr 似乎没有任何理由。如果您只是 return 该函数的值，您将避免所有这些问题：
TGAPicture TGAPicture::loadPicture(const std::string& path) {
// ...
return TGAPicture{pixel, header};
}