Struct help for coordinates?

Hello!

I am making a GPS system. Right now I am trying to set up a way to store coordinates (i.e. latitude and longitude) in variables. I think structs are the way to go?

Im not sure exactly how I can do this with structs though. Im thinking maybe do something like "coord[1].latitude = Lat;".

Here is what I have so far (its not my full code, but just my test code for my webpage):

#include <WiFi.h>
#include <WiFiClient.h>
#include <WebServer.h>
#include <WiFiAP.h>

const char* ssid = "GPSTracker";
const char* password = "GPS";

float HOME_LAT = 0;
float HOME_LON = 0;

WebServer server(80);

struct coords[20] {
  float latitude;
  float longitude;
}
//coords[1].latitude
//Check if header is present and correct
bool is_authentified() {
  Serial.println("Enter is_authentified");
  if (server.hasHeader("Cookie")) {
    Serial.print("Found cookie: ");
    String cookie = server.header("Cookie");
    Serial.println(cookie);
    if (cookie.indexOf("ESPSESSIONID=1") != -1) {
      Serial.println("Authentification Successful");
      return true;
    }
  }
  Serial.println("Authentification Failed");
  return false;
}

//login page, also called for disconnect
void handleLogin() {
  String msg;
  if (server.hasHeader("Cookie")) {
    Serial.print("Found cookie: ");
    String cookie = server.header("Cookie");
    Serial.println(cookie);
  }
  if (server.hasArg("DISCONNECT")) {
    Serial.println("Disconnection");
    server.sendHeader("Location", "/login");
    server.sendHeader("Cache-Control", "no-cache");
    server.sendHeader("Set-Cookie", "ESPSESSIONID=0");
    server.send(301);
    return;
  }
  if (server.hasArg("USERNAME") && server.hasArg("PASSWORD")) {
    if (server.arg("USERNAME") == "admin" &&  server.arg("PASSWORD") == "admin") {
      server.sendHeader("Location", "/");
      server.sendHeader("Cache-Control", "no-cache");
      server.sendHeader("Set-Cookie", "ESPSESSIONID=1");
      server.send(301);
      Serial.println("Log in Successful");
      return;
    }
    msg = "Wrong username/password! try again.";
    Serial.println("Log in Failed");
  }
  String content = "<html><body><form action='/login' method='POST'>Log in to see your GPS Tracker";
  content += "User:<input type='text' name='USERNAME' placeholder='user name'><br>";
  content += "Password:<input type='password' name='PASSWORD' placeholder='password'><br>";
  content += "<input type='submit' name='SUBMIT' value='Submit'></form>" + msg + "<br>";
  server.send(200, "text/html", content);
}

//root page can be accessed only if authentification is ok
void handleRoot() {
  Serial.println("Enter handleRoot");
  String header;
  if (!is_authentified()) {
    server.sendHeader("Location", "/login");
    server.sendHeader("Cache-Control", "no-cache");
    server.send(301);
    return;
  }
  String content = "<html><body><H1>GPS Tracker!</H1><br>";
  content += "<H2>Welcome to your GPS Tracker website!</H2><br>";
  content += "<body>Welcome to your GPS Tracker website!<body><br>";
  content += "<body>Click <a href='/changecoord'>here</a> to change a waypoint.</body><br>";
  content += "<body>Click <a href='/addcoord'>here</a> to add a waypoint.</body><br>";
  content += "<body>Waypoint Latitude: " + String(HOME_LAT,4) + ", Waypoint Longitude: " + String(HOME_LON,4) + "</body></html><br><br><br>";
  if (server.hasHeader("User-Agent")) {
    content += "the user agent used is : " + server.header("User-Agent") + "<br><br>";
  }
  content += "You can access this page until you <a href=\"/login?DISCONNECT=YES\">disconnect</a></body></html>";
  server.send(200, "text/html", content);
}

void handleChangeCoord() {
  String msg;
  if (server.hasHeader("Cookie")) {
    Serial.print("Found cookie: ");
    String cookie = server.header("Cookie");
    Serial.println(cookie);
  }
  
  if (server.hasArg("NUMBER") && server.hasArg("LATITUDE") && server.hasArg("LONGITUDE")) {
    //if (server.arg("LATITUDE") == "admin" &&  server.arg("LONGITUDE") == "admin") {
    String ID = server.arg("NUMBER");
    String Lat = server.arg("LATITUDE");
    String Lon = server.arg("LONGITUDE");
    Serial.println("Latitude " + Lat);
    Serial.println("Longitude " + Lon);
    
    HOME_LAT = Lat.toFloat();
    HOME_LON = Lon.toFloat();

    int ids = ID.toInt();
    coords[ids].latitude = HOME_LAT;

    server.sendHeader("Location", "/");
    server.sendHeader("Cache-Control", "no-cache");
    server.sendHeader("Set-Cookie", "ESPSESSIONID=1");
    server.send(301);
    Serial.println("coordinates done");
    return;
  }
  String content = "<html><body><form action='/changecoord' method='POST'>Type your waypoint ID then type the new coordinates.<br>";
  content += "ID:<input type='text' name='NUMBER' placeholder='ID number'><br>";
  content += "Latitude:<input type='text' name='LATITUDE' placeholder='latitude'><br>";
  content += "Longitude:<input type='text' name='LONGITUDE' placeholder='longitude'><br>";
  content += "<input type='submit' name='SUBMIT' value='Submit'></form>" + msg + "<br>";
  server.send(200, "text/html", content);
}

//no need authentification
void handleNotFound() {
  String message = "File Not Found\n\n";
  message += "URI: ";
  message += server.uri();
  message += "\nMethod: ";
  message += (server.method() == HTTP_GET) ? "GET" : "POST";
  message += "\nArguments: ";
  message += server.args();
  message += "\n";
  for (uint8_t i = 0; i < server.args(); i++) {
    message += " " + server.argName(i) + ": " + server.arg(i) + "\n";
  }
  server.send(404, "text/plain", message);
}

void setup(void) {
  Serial.begin(115200);
  WiFi.softAP(ssid, password);
  IPAddress myIP = WiFi.softAPIP();
  Serial.print("AP IP address: ");
  Serial.println(myIP);


  server.on("/", handleRoot);
  server.on("/login", handleLogin);
  server.on("/changecoord", handleChangeCoord);
  server.on("/addcoord", handleAddCoord);

  server.onNotFound(handleNotFound);
  //here the list of headers to be recorded
  const char * headerkeys[] = {"User-Agent", "Cookie"} ;
  size_t headerkeyssize = sizeof(headerkeys) / sizeof(char*);
  //ask server to track these headers
  server.collectHeaders(headerkeys, headerkeyssize);
  server.begin();
  Serial.println("HTTP server started");
}

void loop(void) {
  server.handleClient();
  delay(2);//allow the cpu to switch to other tasks
}

Any suggestions for how to do that?

Thanks in advance!

Try this to make a 20-element array of the unnamed struct:

struct {
  float latitude;
  float longitude;
} coords[20];
//coords[1].latitude

Hello @johnwasser. Thanks for the quick reply!

How would I use that? Would "coords[1].latitude" still work, and for all twenty latitudes?

Yes. For all 20: 0 through 19.

I think it's working. Thanks!

Trying to find nested struct to no avail

Lol, I changed that.

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