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我試圖挑起一個簡單的狀態模式，下面的一些優秀的教程這裏經過：http://gameprogrammingpatterns.com/state.html狀態模式C++
我通過這個電流教程半路上，我試圖複製的靜態實例每個狀態，通過將它們包含在基類中。但是，當談到切換狀態時，g ++會拋出這個錯誤。
state_test.cpp: In member function ‘virtual void Introduction::handleinput(Game&, int)’:
state_test.cpp:55:16: error: cannot convert ‘Playing*’ to ‘GameState*’ in assignment
game.state_ = &GameState::play;
^
現在，我明白錯誤涉及指針的轉換，但我真的很難看到如何解決它。正如我遵循這個傢伙的代碼，我期望它能夠工作，但是因爲他正在改變它並試圖強化最佳實踐，所以我沒有完整的源代碼可以遵循。但是，在我繼續閱讀本教程的其餘部分之前，我認爲在此階段理解代碼非常重要。
以下是我創建的代碼試圖複製他的國家制度：
#include <iostream>
class Game;
class Introduction;
class Playing;
class GameState
{
public:
static Introduction intro;
static Playing play;
virtual ~GameState() {std::cout << "an undefined GameState has been destroyed" << std::endl;}
virtual void handleinput(Game& game, int arbitary) {}
virtual void update(Game& game) {}
};
class Game
{
public:
Game()
{}
~Game()
{}
virtual void handleinput(int arbitary)
{
state_->handleinput(*this, arbitary);
}
virtual void update()
{
state_->update(*this);
}
//private:
GameState* state_;
};
class Introduction : public GameState
{
public:
Introduction()
{
std::cout << "constructed Introduction state" << std::endl;
}
virtual void handleinput(Game& game, int arbitary)
{
if (arbitary == 1)
game.state_ = &GameState::play;
}
virtual void update(Game& game) {}
};
class Playing : public GameState
{
public:
Playing() {std::cout << "constructed Playing state" << std::endl;}
virtual void handleinput(Game& game, int arbitary)
{
if (arbitary == 0)
game.state_ = &GameState::intro;
}
virtual void update(Game& game) {}
};
int main(int argc, char const *argv[])
{
Game thisgame;
return 0;
}
任何想法，爲什麼我的實現不是編制？
編輯：
所以響應早前輔導，對此我很感激，我修改了代碼。我首先將它們全部放在單獨的文件中，但這比測試代碼量小的代價更麻煩。我簡單地重寫了一個聲明類的頭文件，然後在.cpp文件中定義它們。
這裏是.h文件：
class Introduction;
class Playing;
class Game;
class GameState;
class GameState
{
public:
static Introduction intro;
static Playing play;
virtual ~GameState();
virtual void handleinput(Game& game, int arbitary);
virtual void update(Game& game);
};
class Introduction : public GameState
{
public:
Introduction();
virtual void handleinput(Game& game, int arbitary);
virtual void update(Game& game);
};
class Playing : public GameState
{
public:
Playing();
virtual void handleinput(Game& game, int arbitary);
virtual void update(Game& game);
};
class Game
{
public:
Game();
~Game();
virtual void handleinput(int arbitary);
virtual void update();
GameState* state_;
};
這裏是.cpp文件：
#include <iostream>
#include "state.h"
GameState::~GameState()
{std::cout << "Exiting Game State Instance" << std::endl;}
void GameState::handleinput(Game& game, int arbitary)
{}
void GameState::update(Game& game)
{}
Game::Game()
{}
Game::~Game()
{}
void Game::handleinput(int arbitary)
{
state_->handleinput(*this, arbitary);
}
void Game::update()
{
state_->update(*this);
}
Introduction::Introduction()
{
std::cout << "constructed Introduction state" << std::endl;
}
void Introduction::handleinput(Game& game, int arbitary)
{
if (arbitary == 1)
game.state_ = &GameState::play;
}
void Introduction::update(Game& game) {}
Playing::Playing()
{
std::cout << "constructed Playing state" << std::endl;
}
void Playing::handleinput(Game& game, int arbitary)
{
if (arbitary == 0)
game.state_ = &GameState::intro;
}
void Playing::update(Game& game) {}
int main(int argc, char const *argv[])
{
Game mygame;
return 0;
}
而且我仍然無法得到它的工作。之前的錯誤已經消失，但我正在努力訪問「引入」的靜態實例並在基類內部進行遊戲。拋出的錯誤是：
/tmp/ccH87ioX.o: In function `Introduction::handleinput(Game&, int)':
state_test.cpp:(.text+0x1a9): undefined reference to `GameState::play'
/tmp/ccH87ioX.o: In function `Playing::handleinput(Game&, int)':
state_test.cpp:(.text+0x23f): undefined reference to `GameState::intro'
collect2: error: ld returned 1 exit status
我以爲我有它被懷疑！太沮喪了！
我應該補充一點，RustyX提供的答案確實會編譯，但是我必須將「播放」和「引入」的實例移到類定義之外，然後我不能再將它們設置爲靜態的，我相信這很重要，因爲我只需要每個實例的一個實例，我希望它們儘早初始化。
您可能對我的[STTCL]（https://github.com/makulik/sttcl）框架感興趣。 –