Refer to an array name from variable

vilnis_r · March 28, 2023, 3:53pm

Hi!

My code has several arrays and I am looking to change particular elements of particular arrays. for that reason I have incoming json, that contains all pointers to do so. However I have a problem with referring to an array. So here is the code for the idea what I am looking for:

//This is json message:
{"Array":"targetArr","Place":0,"Value":25}

const char* Array = doc["Array"];
byte Placeholder = doc["Place"];
float newValue = doc["Value"];

//Array[Placeholder] = newValue; //this is general idea of what I am looking for
targetArr[Placeholder] = newValue; //that works fine, except I have to refer to array name directly

I assume there is some syntax matters. I can solve this by using IF statement but I suppose that it is not the shortest way to code. Thanks a lot!

FernandoGarcia · March 28, 2023, 4:23pm

Try this method:

Otherwise post a MRE.

b707 · March 28, 2023, 5:32pm

It is impossible to refer variables by it sourcecode names at runtime. After compiling all names of variables, arrays, structures etc - are stripped from the code, replaced by binary addresses in memory

J-M-L · March 28, 2023, 5:36pm

In that case I'm assuming OP is using the ArduinoJSON library so the syntax for accessing into the document using strings is OK

if the arrays were also in a JSON documents, OP could use the string.

(but it's not the most effective storage unit)

b707 · March 28, 2023, 5:42pm

I don't think so..

As far I see, OP get array name from JSON document, but than try to access an array in program code, not in JSON:

J-M-L · March 28, 2023, 5:48pm

Yes - agreed. May be what I said came off the wrong way

what I'm saying is that if "targetArr" was an entry in a JSON containing all the arrays, OP could use that string to access the array

b707 · March 28, 2023, 5:55pm

Thank you for correction

vilnis_r · March 28, 2023, 6:10pm

Well, I have several arrays in my code that stores settings and with Json messages I send commands to the controller thus changing the values for these different arrays. So far my solution for this is like so:

if (Array == targetArr) {targetArr[Placeholder] = newValue};
if (Array == deviceArr) {deviceArr[Placeholder] = newValue};
// and so on

So my concern is to make this code shorter as this approach produces a lot of similar code lines.

b707 · March 28, 2023, 6:16pm

As I said before, you can't refer variable by name, so your actual solution is a good option. I don't think you can make it shorter.
If you have a lot of such lines, you need to look at how to process them in a batch. Please show the full code for this.

paulpaulson · March 28, 2023, 6:52pm

Take some time and learn how to use data structures. They can also be arranged in arrays.

vilnis_r · March 28, 2023, 7:01pm

Ok, then I'll live with that. I do not think that batch will be needed - so far I have some 4 arrays that could be updated via json so not a very big deal for batch. Just wanted a bit cleaner code. I am always suspicious when something similar repeats. My code is far from complete so I am still experimenting.

/*********
  reads ds18d20 on GPIO 15
  publish & receive from MQTT
*********/

#include <OneWire.h>
#include <DallasTemperature.h>
#include <WiFi.h>
#include <PubSubClientL.h>
#include <ArduinoJson.h>
#include <Preferences.h>

Preferences prefs;
// Data wire is plugged TO GPIO 15
#define ONE_WIRE_BUS 15

// Setup a oneWire instance to communicate with any OneWire devices (not just Maxim/Dallas temperature ICs)
OneWire oneWire(ONE_WIRE_BUS);

// Pass our oneWire reference to Dallas Temperature. 
DallasTemperature sensors(&oneWire);

// Number of temperature devices found
int numberOfDevices;

// We'll use this variable to store a found device address
DeviceAddress tempDeviceAddress; 


// Update these with values suitable for your network.
const char* ssid = "wi-fi";
const char* password = "";
const char* mqtt_server = "172.16.0.14";
const char* TOPIC = "Bruzis";
WiFiClient espClient;
PubSubClient client(espClient);
static char payload[1536];
#define MSG_BUFFER_SIZE  (1536)
char msg[MSG_BUFFER_SIZE];

unsigned long lastMsg = 0;

//SETTINGS MATRIX (14 relays)

int i;

//digital sensor ID address HEX
uint8_t T_ID_Arr[14][8] = {
  {0x28,0xCC,0x44,0xAD,0x5F,0x20,0x01,0x85},
  {0x28,0x6D,0x00,0x25,0x5F,0x20,0x01,0xDD},
  {0x28,0x16,0x43,0x10,0x5F,0x20,0x01,0xD3},
  {0,0,0,0,0,0,0,0},
  {0,0,0,0,0,0,0,0},
  {0,0,0,0,0,0,0,0},
  {0,0,0,0,0,0,0,0},
  {0,0,0,0,0,0,0,0},
  {0,0,0,0,0,0,0,0},
  {0,0,0,0,0,0,0,0},
  {0,0,0,0,0,0,0,0},
  {0,0,0,0,0,0,0,0},
  {0,0,0,0,0,0,0,0},
  {0,0,0,0,0,0,0,0}
};

byte relayArr [14] = {5, 19, 18, 17, 16, 0, 0, 0, 0, 0, 0, 0, 0, 0}; //corresponding relay pins
byte relayStatusArr[14] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}; //relay high/low status, 0 at the start
byte deviceArr[14] = {1, 1, 1, 2, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0}; //device code, 1-probe, 2-device, 0-unpopulated
byte logicArr[14] = {1,1,2,0,0,0,0,0,0,0,0,0,0,0}; //device logic, 1-up, 2-down, 0-unpopulated

//device pin matrix
byte D_relay_Arr[14][14] = {
  {0,0,0,0,0,0,0,0,0,0,0,0,0,0},
  {0,0,0,0,0,0,0,0,0,0,0,0,0,0},
  {0,0,0,0,0,0,0,0,0,0,0,0,0,0},
  {1,0,0,0,0,0,0,0,0,0,0,0,0,0},
  {0,1,1,0,0,0,0,0,0,0,0,0,0,0},
  {0,0,0,0,0,0,0,0,0,0,0,0,0,0},
  {0,0,0,0,0,0,0,0,0,0,0,0,0,0},
  {0,0,0,0,0,0,0,0,0,0,0,0,0,0},
  {0,0,0,0,0,0,0,0,0,0,0,0,0,0},
  {0,0,0,0,0,0,0,0,0,0,0,0,0,0},
  {0,0,0,0,0,0,0,0,0,0,0,0,0,0},
  {0,0,0,0,0,0,0,0,0,0,0,0,0,0},
  {0,0,0,0,0,0,0,0,0,0,0,0,0,0},
  {0,0,0,0,0,0,0,0,0,0,0,0,0,0}
};

// User temperature settings
float targetArr[14];
float deltaArr[14]={1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};

//float targetArrS[14]={26, 26, 26, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
//float deltaArrS[14]={1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};


// END of declarations -------------------------------------------------------------------------------

void setup_wifi() {

   // We start by connecting to a WiFi network
  Serial.println();
  Serial.print("Connecting to ");
  Serial.println(ssid);

  WiFi.mode(WIFI_STA);
  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  randomSeed(micros());

  Serial.println("");
  Serial.println("WiFi connected");
  Serial.println("IP address: ");
  Serial.println(WiFi.localIP());
}

// This function handles received command messages
void myMessageArrived(char* topic, byte* payload, unsigned int length) {
  // Convert the message payload from bytes to a string
  String message = "";
  for (unsigned int i=0; i< length; i++) {
    message = message + (char)payload[i];
  }
  // Print the message to the serial port
  Serial.print("Incoming message: ");
  Serial.println(message);

// extract values from incoming Json
StaticJsonDocument <256> doc;
deserializeJson(doc,payload);

String Array = doc["Array"];
byte Placeholder = doc["Place"];
float newValue = doc["Value"];

//Array[Placeholder] = newValue; does not work?!
if (Array == "targetArr") {targetArr[Placeholder] = newValue}
if (Array == "deltaArr") {deltaArr[Placeholder] = newValue}
// add some later  
}

void reconnect() {
  // Loop until we're reconnected
  while (!client.connected()) {
    Serial.print("Attempting MQTT connection...");
    // Create a random client ID
    String clientId = "ESP32Client-";
    clientId += String(random(0xffff), HEX);
    // Attempt to connect
    if (client.connect(clientId.c_str())) {
      Serial.println("connected");
      
      // mqtt topic for incoming commands
      client.subscribe("ESP_in");
      
    } else {
      Serial.print("failed, rc=");
      Serial.print(client.state());
      Serial.println(" try again in 5 seconds");
      // Wait 5 seconds before retrying
      delay(5000);
    }
  }
}

// function to print a device address
void printAddress(DeviceAddress deviceAddress) {
  for (uint8_t i = 0; i < 8; i++){
    if (deviceAddress[i] < 16) Serial.print("0");
      Serial.print(deviceAddress[i], HEX);
    }
}

// function to get a device address as String
String formatAddress(DeviceAddress deviceAddress)
{
  String Address;
  for (uint8_t i = 0; i < 8; i++)
  {
    if (deviceAddress[i] < 16) Address = Address + "0";
    Address = Address + String(deviceAddress[i], HEX);
  }
  Serial.println();
  Serial.println(Address);
  return Address;
}

void setup(){
  
  delay(1000);
  // start serial port
  Serial.begin(115200);

  prefs.begin("targetArr"); //namespace
  //bytes can be put/get in namespace directly see prefs2struct example
  //prefs.putBytes("targetArr", (byte*)(&targetArrS), sizeof(targetArrS));
  prefs.getBytes("targetArr", &targetArr, sizeof(targetArr));

  setup_wifi();
client.setServer(mqtt_server, 1883);
client.setCallback(myMessageArrived); //initializes incoming commands
  // Start up the library
  sensors.begin();
  
  // Grab a count of devices on the wire
  numberOfDevices = sensors.getDeviceCount();
  
  // locate devices on the bus
  Serial.print("Locating devices...");
  Serial.print("Found ");
  Serial.print(numberOfDevices, DEC);
  Serial.println(" devices.");

  // Loop through each device, print out address
  for(int i=0;i<numberOfDevices; i++){
    // Search the wire for address
    if(sensors.getAddress(tempDeviceAddress, i)){
      Serial.print("Found device ");
      Serial.print(i, DEC);
      Serial.print(" with address: ");
      printAddress(tempDeviceAddress);
      //Serial.println(tempDeviceAdress, DEC);
      Serial.println();
    } else {
      Serial.print("Found ghost device at ");
      Serial.print(i, DEC);
      Serial.print(" but could not detect address. Check power and cabling");
    }
  }

// Set up the relay outputs, and start them with LOW

 for (i = 0; i < 14; i++) {
  pinMode(relayArr[i], OUTPUT);
  digitalWrite(relayArr[i], LOW);
 }
   
}

//---------------------------------------------------
void cool (float tempC, int i)
{
    // need probe check if exists
        
    if(relayStatusArr[i] == 0 and tempC >= targetArr[i] + deltaArr[i]){
    digitalWrite(relayArr[i], 1);
    relayStatusArr[i] = 1;
    }
    if(relayStatusArr[i] == 1 and tempC <= targetArr[i]){
    digitalWrite(relayArr[i], 0);
    relayStatusArr[i] = 0;
    }

}
//---------------------------------------------------
void heat (float tempC, int i)
{
    if(relayStatusArr[i] == 0 and tempC <= targetArr[i] - deltaArr[i]){
    digitalWrite(relayArr[i], 1);
    relayStatusArr[i] = 1;
    }
    if(relayStatusArr[i] == 1 and tempC >= targetArr[i]){
    digitalWrite(relayArr[i], 0);
    relayStatusArr[i] = 0;
    }

}
//---------------------------------------------------
void PumpStatusCheck(int index)
{
  relayStatusArr[index] = 0;
  for (int a = 0; a < 14; a++) {
  if (D_relay_Arr[index][a] != 0) {
  relayStatusArr[index] |= relayStatusArr[a];
  }
  }
  digitalWrite(relayArr[index], relayStatusArr[index]);
}


void loop(){ 
  if (!client.connected()) {
    reconnect(); // maintain MQTT connection
  } 
  client.loop(); 

sensors.requestTemperatures();
    
for (i = 0; i < 14; i++) {
  if (deviceArr[i] == 1){ // detect probe mark in array
    //check if sensor exists
    float tempC = sensors.getTempC(T_ID_Arr[i]);
      if (logicArr[i] == 1) {
      heat(tempC, i);  
      }
      else if (logicArr[i] == 2){
      cool(tempC, i);
      }
  } else if (deviceArr[i] == 2){ //detect device mark in array
  PumpStatusCheck (i);
  }
}

long now = millis();
  if (now - lastMsg > 50000) {
    lastMsg = now;
    DynamicJsonDocument doc(1536); // maximum size for 14 boxes is recomended 1536 (min 1120)
    
  for (i = 0; i < 14; i++) {
  if (deviceArr[i] == 1){ // detect probe mark in array
    //check if sensor exists
    float tempC = sensors.getTempC(T_ID_Arr[i]);
    doc[String(i)]["T"]=round(tempC*10)/10;
    doc[String(i)]["R"]=digitalRead(relayArr[i]);
    doc[String(i)]["P"]=targetArr[i];
    doc[String(i)]["L"]=int(logicArr[i]);  
  } else if (deviceArr[i] == 2){ //detect device mark in array
    doc[String(i)]["R"]=digitalRead(relayArr[i]);
  }
}
delay(1000);
serializeJsonPretty(doc, payload);
client.publish("B_Status", payload);
//serializeJsonPretty(doc, Serial);
//Serial.println();

}
}

camsysca · March 28, 2023, 8:45pm

A quick glance at your code makes me think you need an array of 14 structs. Have you considered that, and how you would work with it in your code?

vilnis_r · March 28, 2023, 9:06pm

To be honest I am not very familiar with array of structs. I looked at them when thought about saving settings into Preferences (memory) but found a bit complicated them at that moment so I switched to other problems. But yes, I had overall idea that putting all my separate arrays into one structure could be reasonable way to do. I have to learn them in order to get them work in my code.

paulpaulson · March 29, 2023, 4:48am

Hello vilnis_r

Take a view to gain then knowledge.

Have a nice day and enjoy coding in C++.

system · September 25, 2023, 4:49am

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Refer to an array name from variable

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