c++ - 公开定义对象，但在构造函数中创建它

Question

我想做的与此类似(工作):

class Claw {
  public:
    Claw(int pin);
  private:
    int pin;
  };

Claw::Claw(int pinNumber) {
  pin = pinNumber;
  }

但我想用类而不是基本类型来做。我想在私有(private)部分定义类(这样我就可以在所有对象上使用它)并在 Wheel 构造函数中执行 AccelStepper 构造函数。我已经尝试了这两种解决方案，但它们都给出了不同的错误:

class Wheel {
  public:
    Wheel(int pin);
  private:
    AccelStepper stepper;
  };

Wheel::Wheel(int pinNumber) {

  // This doesn't work
  AccelStepper stepper(AccelStepper::DRIVER, pinNumber, 1);

  // This also doesn't work
  stepper(AccelStepper::DRIVER, pinNumber, 1);
  }

我怎样才能实现我想做的事情？

请注意，这有效，但我无法传递 PIN 码:

class Wheel {
  public:
    Wheel();
  private:
    AccelStepper stepper(5);
  };

Wheel::Wheel() {
  }

Answer 1

你用 member initialization list 来做:

Wheel::Wheel(int pinNumber)
    : stepper(AccelStepper::DRIVER, pinNumber, 1)
{
}