C ++为每个，从向量元素 [英] C++ for each, pulling from vector elements

问题描述

我想要对一个攻击向量做一个foreach，每个攻击都有一个唯一ID ，1-3。

类方法接受1-3的键盘输入。

我试图使用foreach来运行我的元素在m_attack，看看数字是否匹配，如果它

我看到的问题是：

  a'for each'语句不能对类型为std :: vector< Attack 
 的表达式进行操作

$ b b

我是这样完全错了，我有C＃的经验，是一种基于我的基础上，任何帮助将不胜感激。

我的代码如下：

在标题中

 向量< Attack> m_attack; 
  

在班级

  int Player :: useAttack（int input）
 {
 
每个（攻击*攻击m_attack）//问题部分
 {
 //用于以下操作的伪指令
 if（attack-> m_num == input）
 {
 //对于发现的攻击，损害
 attack-> makeDamage （）; 
} 
} 
} 
  

解决方案>

如果你的编译器支持基于C ++ 11范围的for循环，那么代码如下：

  （auto& attack：m_attack）//通过引用访问以避免复制
 {
 if（attack-> m_num == input）
 {
 attack-> makeDamage （）; 
} 
} 
  

您应该使用 const auto & attack 取决于 makeDamage（）的行为。

我假设你在Windows上开发基于你的C＃背景和警告消息，在这种情况下基于范围的for循环仅在Visual Studio 2012中可用。如果您在Visual Studio 2010中工作，请参阅 andre的回答使用 std :: for_each 在< algorithm> 标题中找到。

如果您不满意使用 std :: for_each ，您可以使用迭代器循环 m_attack ：

  for（auto attack = m_attack.begin（）; attack！= m_attack.end（）; ++ attack）
 {
 if（attack-> m_num == input）
 {
 attack-> makeDamage（）; 
} 
} 
  

使用 m_attack.cbegin ）和 m_attack.cend（）以获取 const 迭代器。 b $ b

I am trying to do a foreach on a vector of attacks, each attack has a unique ID say, 1-3.

The class method takes the keyboard input of 1-3.

I am trying to use a foreach to run through my elements in m_attack to see if the number matches, if it does... do something.

The problem I'm seeing is this:

a'for each' statement cannot operate on an expression of type "std::vector<Attack

Am I going about this totally wrong, I have C# experience and is kind of what I'm basing this on, any help would be appreciated.

My code is as follows:

In header

vector<Attack> m_attack;

In class

int Player::useAttack (int input)
{

    for each (Attack* attack in m_attack) // Problem part
    {  
        //Psuedo for following action
        if (attack->m_num == input)
        {
            //For the found attack, do it's damage
            attack->makeDamage();
        }
    }
}

解决方案

If your compiler supports C++11 ranged-based for loops, then the code is as follows:

   for (auto &attack : m_attack) // access by reference to avoid copying
    {  
        if (attack->m_num == input)
        {
            attack->makeDamage();
        }
    }

You should use const auto &attack depending on the behavior of makeDamage().

Side note: I assume you're developing on Windows based on your C# background and warning message, in which case the range-based for loop is only available in Visual Studio 2012. If you are working in Visual Studio 2010, see andre's answer for using std::for_each found in the <algorithm> header.

If you are uncomfortable using std::for_each, you can loop over m_attack using iterators:

   for (auto attack = m_attack.begin(); attack != m_attack.end(); ++attack)
    {  
        if (attack->m_num == input)
        {
            attack->makeDamage();
        }
    }

Use m_attack.cbegin() and m_attack.cend() to get const iterators.

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