c++ - 在 C++ (arduino) 中，我如何使用一个字段来构建另一个字段

Question

我正在尝试创建这个头文件:

#define MqttConfig_h

#include "Arduino.h"
#include <PubSubClient.h>         // MQTT client
#include <ESP8266WiFi.h>      // ESP8266 Core WiFi Library
#include <Config.h>

class MqttConfig
{
  public:
    MqttConfig();
    void initMQTT();

  private:
    String _mqttServer;
    String _mqttPrefix;
    WiFiClient _wifi;
    PubSubClient _mqttClient(_wifi);     ****** ERROR HERE  *******
};

#endif

我已经尝试了各种方法让它工作:

// This seemed logical to me
PubSubClient _mqttClient(WiFiClient{});

// This was an attempt to read the field and pass it back
WiFiClient GetWiFiClient();       
PubSubClient _mqttClient(GetWiFiClient());

// This compiles, but does something I don't understand
WiFiClient GetWiFiClient();       
PubSubClient _mqttClient(WiFiClient);

在头文件中“链接字段”的正确方法是什么？我会注意到我不关心对 _wifi 对象的引用，我之所以这样做是因为 PubSubClient 对象的构造函数需要它..

Answer 1

通常，您在构造函数中初始化字段:

class MqttConfig
{
  public:
    MqttConfig();

  private:
    PubSubClient _mqttClient;
};

// ...
MqttConfig::MqttConfig()
    : _mqttClient(WiFiClient{})
{
}

---

至于你最后的尝试:

// This compiles, but does something I don't understand
WiFiClient GetWiFiClient();       
PubSubClient _mqttClient(WiFiClient);

这些是方法声明。