Question

我是c +的新手。我有一个简单的控制台应用程序，header.h保存我的班级

class MyClass
{
public:
    float x, y, z;

    MyClass(float x, float y, float z);
};

我有implement.cpp我所有已实施的方法，我有

MyClass::MyClass(float x, float y, float z) {};

然后在main.cpp我尝试简单地打印值

int main()
{
  MyClass One(-3.0f, 0.0f, 4.0f);

  cout <<  "Firsth Object: " << One.x << ", " << One.y << ", " << One.z << endl;
}

但是在控制台值中打印如下：

-1.07374e + 08，-1.07374e + 08，-1.07374e + 08

我做错了什么？

Answer 1

您的构造函数未初始化任何成员：> var resolve1, resolve2; > var promise1 = new Promise(function(r){ resolve1 = r; }); > var thenable = {then:function(r) { console.log(...arguments); resolve2 = r; }}; > resolve1(thenable); undefined // you'd expected a call to the then method here > promise1 Promise {[[PromiseStatus]]: "resolved", [[PromiseValue]]: Object} > thenable Object {} > resolve2(42) Uncaught TypeError: resolve2 is not a function(…) // uh. yeah. > promise1.then(x => console.log(x)) () { [native code] }, () { [native code] } // ah there was the call, even with a resolver Promise {[[PromiseStatus]]: "pending", [[PromiseValue]]: undefined} > resolve2(42) 42 undefined > promise1.then(x => console.log(x)) () { [native code] }, () { [native code] } // but now they fucked up. // Instead of another call on the thenable, you'd expected the result to be logged Promise {[[PromiseStatus]]: "pending", [[PromiseValue]]: undefined} > resolve2(42) 42 // OMG. undefined，MyClass::x或MyClass::y。

你必须这样做：

MyClass::z

或更好（更惯用，可能更快）：

MyClass::MyClass(float x, float y, float z)
{
    this->x = x;
    this->y = y;
    this->z = z;
};

如果没有，您将打印MyClass::MyClass(float x, float y, float z) : x( x ), y( y ), z( z ) { };对象MyClass的未初始化成员的值。一般情况下，您必须always initialize members of a class才能使用它们。

Answer 2

你当前的构造函数什么也没做。

您必须初始化对象变量。为此你可以使用

TranslatableRoute::resource('recipe', 'recepten', 'RecipeController');

构造函数中的这种类型的初始化称为初始化列表，您可以读取它here。

这与@ jpo38指出的构造函数具有相同的效果。

c ++ float作为参数传递未正确打印

2 个答案: