Questions about const

[CloneWolf-Jiang]

Sorry, I don't speak English..............

Code:

struct WIFI_List_Struct {
  const size_t bufferSize = JSON_OBJECT_SIZE(6) + 64;
  String SSID;
  String MAC;
  int Channel;
  bool isHidden;
  int RSSI;
  String Encrypt;

  void save(const JsonVariant &obj);
  void load(JsonVariant &obj) const;
};


struct WIFI_Scan_Struct {
  int State;
  int Num;
  ArrayList<WIFI_List_Struct> WIFI_List;


  void save(const JsonVariant &obj);
  void load(JsonVariant &obj) const;
};

Error:

sketch\ArrayList.h: In instantiation of 'bool ArrayList<T>::reallocate(size_t) [with T = WIFI_List_Struct; size_t = unsigned int]':

sketch\ArrayList.h:36:9:   required from 'ArrayList<T>::ArrayList() [with T = WIFI_List_Struct]'

sketch\WIFI_Scan.h:22:8:   required from here
ArrayList.h:285:29: error: use of deleted function 'WIFI_List_Struct& WIFI_List_Struct::operator=(const WIFI_List_Struct&)'

  285 |                 newBlock[i] = m_Data[i];
      |                 ~~~~~~~~~~~~^~~~~~~~~
exit status 1

[wachidsusilo]

Looks like the assignment operator has been deleted in your class. Is that all of your code?

I will investigate your code later.

[CloneWolf-Jiang]

Yes, when const exists in struct, the compiler reports an error

[CloneWolf-Jiang]

Thanks

[wachidsusilo]

@CloneWolf-Jiang I have tried your code using my latest implementation of this library. It's compiled without error. I will push a commit after this.

UPDATE:
The repo has been updated. Your code was compiled on ESP32 but not on Arduino UNO. Looks like the Arduino compiler does not happy with your code. I'll give you a solution if you tell me what you want to achieve.

UPDATE 2:
The reason the compiler implicitly deletes copy assignment and move assignment operator is because it can't copy const member. The solution is just explicitly defining copy and move assignment operator.

struct WIFI_List_Struct {
    const size_t bufferSize = JSON_OBJECT_SIZE(6) + 64;
    String SSID;
    String MAC;
    int Channel;
    bool isHidden;
    int RSSI;
    String Encrypt;

   // Copy assignment operator
    WIFI_List_Struct& operator=(const WIFI_List_Struct& other) {
        SSID = other.SSID;
        MAC = other.MAC;
        Channel = other.Channel;
        isHidden = other.isHidden;
        RSSI = other.RSSI;
        Encrypt = other.Encrypt;
        return *this;
    }

   // Move assignment operator
    WIFI_List_Struct& operator=(WIFI_List_Struct&& other) {
        SSID = other.SSID;
        MAC = other.MAC;
        Channel = other.Channel;
        isHidden = other.isHidden;
        RSSI = other.RSSI;
        Encrypt = other.Encrypt;
        return *this;
    }

    void save(const JsonVariant &obj);
    void load(JsonVariant &obj) const;
};

[wachidsusilo]

@CloneWolf-Jiang Does my solution resolve your issue?