c++ - 带类(class)的二十一点模拟器

Question

我是 C++ 的新手，正在尝试制作 Blackjack 模拟器。 Player 是一个类，用于存储从一副牌中发出的牌； Card 类包含花色和面值。我不断收到 Card Player::getCard( int index ) const 的错误消息“Control may reach end of non-void function”，我做错了什么？也有人可以检查我的代码中是否存在任何逻辑缺陷，因为我无法运行它并由于错误消息而无法检查？

#include "Player.h"
#include "Game.h"
#include "Card.h"
using namespace std;

Player::Player( )
{
    // The Player has no Cards in his hand
    myNumberOfCards = 0;
}

std::ostream& operator <<( std::ostream& outs, const Player & p )
{
    // print out all the actual cards in the array myCards
    for (int i = 0; i < p.cardCount(); i++)
    {
        outs << p.myCards[i] << endl;
    }
    return( outs );
}

void Player::acceptCard(Card c)
{
    // as long as there is space in the array myCards, place Card c into myCards
    //        if there is not enough space for another card, throw an exception
    try
    {
        for (; myNumberOfCards < MAXCARDS; myNumberOfCards++)
            myCards[ myNumberOfCards ] = c;
        if (myNumberOfCards > MAXCARDS)
            throw myNumberOfCards;
    }
    catch (int e)
    {
        std::logic_error( "more than maximum of cards possible" ); // Since the player must be busted if he has more than 11 cards, how should I set the outcome to playerbusted if I have a bool in the game class?
    }
}

Card Player::getCard( int index ) const
{
    // return the requested card
    // if the index is bad, throw an exception
    try
    {
        while ( index > 0 && index < myNumberOfCards )
            return ( myCards[ index ] );
        if (index < 0 || index > myNumberOfCards)
            throw index;
    }
    catch (int e)
    {
        std::logic_error( "bad index" ); // why there's an error?
    }
}

int Player:: cardCount() const
{
    //  return the number of cards stored in my array
    return myNumberOfCards;
}

int  Player::handcount( ) const
{
    // total up the points in this player's hand
    // Ace's might be worth 1 or 11
    Player p;
    int total = 0;
    bool hasAce = false;
    for (int i = 0; i < myNumberOfCards; i++)
    {
        total += myCards[i].count();
        if (myCards[i].getFace() == ACE)
            hasAce = true;
    }
    if (total < 11 && hasAce == true)
        total += 10;
    return( total );
}


bool Player::hasBlackJack( ) const
{
    bool result = false;
    if (myNumberOfCards == 2 && handcount() == 21)
    {
        result = true;
    }
    return( result );
}

Answer 1

// vvvv must return a Card
   Card Player::getCard( int index ) const
{
    try
    {
        // ...
            throw index;
    }
    catch (int e)
    {
        std::logic_error( "bad index" ); // this doesn't throw, so will continue past
    }
    // ends up here, doesn't return
}

你不会抛出一个std::logic_error，只是在适当的地方构造一个然后什么也不做。

如果发生命中throw index 的错误，您最终会到达函数底部而不返回任何内容，即Undefined Behaviour。 (非常糟糕，任何事情都有可能发生)。

可能您的意思是throw std::logic_error("bad index");？这会导致您异常退出函数，而不是正常返回，因此不会导致问题。

去掉getCard中的try/catch，替换

会更简单

throw index;

与

throw std::logic_error("bad index");

因为调用者的最终结果是相同的。并放弃 while，因为它实际上不是一个循环，只是一个检查。这是简化版本:

Card Player::getCard( int index ) const
{
    // return the requested card
    // if the index is bad, throw an exception
    if ( index > 0 && index < myNumberOfCards )
        return ( myCards[ index ] );
    else
        throw std::logic_error("bad index");
}

您在 acceptCard 中犯了同样的错误，但由于它返回 void，您看不到错误消息:“falling off the bottom” of a void 函数是允许的，它就像最后一行只是 return; 一样。

---

此外，请重新考虑您使用的不良做法 using namespace std;和 endl .