我的子类的属性是惰性初始化的 我在C++和一个子类中创建了一个父类，它有两个属性：为了使用我的子类，我声明它，并将它的地址分配给父类的指针。因此，我使用父类的方法

我的问题是：当我使用cyclePulse方法时，没有参数int trigger、int echo和类_trigger和_echo中的属性，该方法无法正常工作。我想这是因为属性_trigger和_echo是惰性初始化的，或者是因为我在创建对象时没有使用new关键字

class ISensor {
...
public:
    ISensor();
    virtual ~ISensor();
    ...
    virtual int connect() = 0;
    virtual char * readRequest() = 0;
    virtual int disconnect() = 0;
};

class HCSR04: public ISensor {
private:
    int _trigger;
    int _echo;
public:
    HCSR04();
    HCSR04(int trigger, int echo);
    ...
    int connect();
    char * readRequest();
    uint64_t cyclePulse(int trigger, int echo);
    float distanceCentimeters();
};

下面是HCSR04.cpp的实现。编辑：我忘记了构造函数

HCSR04::HCSR04() {
    _echo = RPI_V2_GPIO_P1_13;
    _trigger = RPI_V2_GPIO_P1_15;
}
HCSR04::HCSR04(int trigger, int echo) {
    _echo = echo;
    _trigger = trigger;
}    
char * HCSR04::readRequest() {
    float preCent = distanceCentimeters();
    char* buf = new char[20];
    sprintf(buf, "%.10f", preCent);
    return buf;
}
float HCSR04::distanceCentimeters() {
    return (float) cyclePulse(_trigger, _echo) / 55.5;
}
uint64_t HCSR04::cyclePulse(int trigger, int echo) {
    uint64_t width, begin, start, end;
    int max = 80, check;

    begin = bcm2835_st_read();

    // Emit pulse for 10 microseconds
    bcm2835_gpio_write(_trigger, HIGH); // Set trigger state HIGH
    bcm2835_delayMicroseconds(10);  // Wait 10 microseconds
    bcm2835_gpio_write(_trigger, LOW);  // Set trigger state LOW

    while (bcm2835_gpio_lev(_echo) == LOW && check < max) {
        start = bcm2835_st_read();
        check = (int) begin - start;
    }
    while (bcm2835_gpio_lev(_echo) == HIGH) {
        bcm2835_delayMicroseconds(1);
    }
    end = bcm2835_st_read();

    width = end - start;

    return width;
}

---

这里给出我之前的评论作为可能的答案，因为我假设未初始化的变量导致了您的错误：

uint64_t HCSR04::cyclePulse(int trigger, int echo) {
    uint64_t width, begin, start, end;
    int max = 80, check = 0;  // <<< init check to 0. 
                              // Btw: size_t or any other unsigned type matches
                              // better the purpose of what you want to achieve.

    begin = bcm2835_st_read();

    // begin is not used afterwards. Did you mean to initialize "start" here?
    start = begin;

    // Emit pulse for 10 microseconds
    bcm2835_gpio_write(_trigger, HIGH); // Set trigger state HIGH
    bcm2835_delayMicroseconds(10);  // Wait 10 microseconds
    bcm2835_gpio_write(_trigger, LOW);  // Set trigger state LOW

    while (bcm2835_gpio_lev(_echo) == LOW && check < max) {
        start = bcm2835_st_read();
        check = (int) begin - start;
    }
    while (bcm2835_gpio_lev(_echo) == HIGH) {
        bcm2835_delayMicroseconds(1);
    }
    end = bcm2835_st_read();

    width = end - start;

    return width;
}

---

HCSR04s构造函数？在不接受任何参数的构造函数中，您将_trigger和_echo设置为什么？我编辑了消息。很抱歉。我忘记了构造器。但是我正在初始化构造函数上的attr。什么意思是不能正常工作？它是如何正常工作的？我在代码中没有看到任何延迟初始化。但是您正在cyclePulse方法中使用check uninitialized。这可能导致提前致电bcm2835_st__read

uint64_t HCSR04::cyclePulse(int trigger, int echo) {
    uint64_t width, begin, start, end;
    int max = 80, check = 0;  // <<< init check to 0. 
                              // Btw: size_t or any other unsigned type matches
                              // better the purpose of what you want to achieve.

    begin = bcm2835_st_read();

    // begin is not used afterwards. Did you mean to initialize "start" here?
    start = begin;

    // Emit pulse for 10 microseconds
    bcm2835_gpio_write(_trigger, HIGH); // Set trigger state HIGH
    bcm2835_delayMicroseconds(10);  // Wait 10 microseconds
    bcm2835_gpio_write(_trigger, LOW);  // Set trigger state LOW

    while (bcm2835_gpio_lev(_echo) == LOW && check < max) {
        start = bcm2835_st_read();
        check = (int) begin - start;
    }
    while (bcm2835_gpio_lev(_echo) == HIGH) {
        bcm2835_delayMicroseconds(1);
    }
    end = bcm2835_st_read();

    width = end - start;

    return width;
}