c++ - 为什么我的if else语句不起作用并从数组中输出正确的索引？

Question

该代码应该从用户输入中输出正确的颜色。用户的输入存储在数组中。但是，else语句未执行/工作。

string eyecolor;
string colorcin[4];

void color() {
  cout << "I am going to ask you for 4 colors." << endl;
  for (int a = 0; a < 4; a++) {
    cout << "Color " << a + 1 << ": ";
    cin >> colorcin[a];
  }
}

void eyes() {
  cout << "What color are your eyes? ";
  cin >> eyecolor;
  if (eyecolor == "blue" || "Blue" || "green" || "Green" || "hazel" ||
      "Hazel") {
    cout << "Your favorite color is " << colorcin[0] << endl;
  } else {
    cout << "Your favorite color is " << colorcin[1] << endl;
  }
}

int main() {
  color();
  eyes();
}

Answer 1

这不是您比较多个值的方式:

if (eyecolor == "blue" || "Blue" || "green" || "Green" || "hazel" ||
      "Hazel") {

这实际上是先比较 eyecolor和 "blue"。如果为假，则在 bool(boolean) 上下文中评估 "Blue"。由于它是一个字符串常量，因此它会衰减为指向其第一个元素的指针，并且由于该指针不能为 NULL，因此其求值为true，因此此表达式将始终为true。

您需要显式比较 eyecolor和每个可能的值:

if (eyecolor == "blue" || eyecolor == "Blue" || eyecolor == "green" || 
    eyecolor == "Green" || eyecolor == "hazel" || eyecolor == "Hazel") {

与 haircolor相同。