How to add a yield before else if?

Question

So I am running my project on a NodeMCU, but I don't know how to let it add a yield in front of an else if. It will give me an error like this:

Arduino:1.8.12 (Windows 10), 開發板:"NodeMCU 1.0 (ESP-12E Module), 80 MHz, Flash, Legacy (new can return nullptr), All SSL ciphers (most compatible), 4MB (FS:2MB OTA:~1019KB), 2, v2 Lower Memory, Disabled, None, Sketch + WiFi Settings, 115200"

G:\資優班\科展\程式碼\Front_End\Main_Code_V5\Main_Server\Main_Server.ino: In function 'void loop()':

Main_Server:84:5: error: 'else' without a previous 'if'

exit status 1 'else' without a previous 'if'

This report would have more information with "Show verbose output during compilation" option enabled in File -> Preferences.

Here's the code:

#include <SPI.h>
#include <ESP8266WiFi.h>
#define MAX_SRV_CLIENTS 2
#define led LED_BUILTIN
WiFiServer server(80);
WiFiClient serverClients[MAX_SRV_CLIENTS];
IPAddress ip(10, 241, 241, 27);
IPAddress mask(255, 255, 255, 0);
IPAddress gateway(10, 241, 241, 254);
char ssid[] = "AP";
char pass[] = "Science_Fair";
void setup() {
 Serial.begin(9600);
 WiFi.config(ip, gateway, mask);
 WiFi.begin(ssid, pass);
 while (WiFi.status() != WL_CONNECTED) {
 yield();
 }
 server.begin();
 pinMode(led, OUTPUT);
 digitalWrite(led, LOW);
}
void loop() {
 uint8_t i;
 Serial.setTimeout(10);
 for (i = 0; i < MAX_SRV_CLIENTS; i++) {
 Serial.println("Pre 1");
 if (server.hasClient()) {
 Serial.println("Pre 2");
 if (!serverClients[i] || !serverClients[i].connected()) {
 Serial.println("Pre 3");
 if (serverClients[i]) {
 Serial.println("Pre 4");
 serverClients[i].stop();
 Serial.println("Pre 5");
 }
 Serial.println("Pre 6");
 serverClients[i] = server.available();
 Serial.println("Pre 7");
 serverClients[i].setTimeout(10);
 Serial.println("Pre 8");
 Serial.print("New client: ");
 Serial.println("Pre 9");
 Serial.println(i);
 Serial.println("Pre 10");
 break;
 }
 }
 yield();
 }
 for (i = 0; i < MAX_SRV_CLIENTS; i++) {
 String fromClient = serverClients[i].readStringUntil('e');
 Serial.println("P1");
 yield();
 if (fromClient == "LR") {
 Serial.println("LR");
 String reply = Serial.readStringUntil('e');
 Serial.println("P2");
 yield();
 if (reply == "Warn_B") {
 yield();
 Serial.println("Confirm");
 Serial.println("P3");
 for (i = 0; i < MAX_SRV_CLIENTS; i++) {
 serverClients[i].print("Warn_B");
 Serial.println("P4");
 yield();
 }
 }
 }
 yield(); // this is the yield I need to add
 else if (fromClient == "RR") {
 Serial.println("RR");
 Serial.println("P5");
 String reply = Serial.readStringUntil('e');
 Serial.println("P6");
 yield();
 if (reply == "Warn_A") {
 Serial.println("P7");
 Serial.println("Confirm");
 }
 for (i = 0; i < MAX_SRV_CLIENTS; i++) {
 serverClients[i].print("Warn_A");
 Serial.println("P8");
 yield();
 }
 }
 yield();
 }
}

I need the yield() there but I don't know how to let it still do the else if. Please help me guys, thanks!

• Majenko: Why do you think you need a yield there?
• Ted Lu: @Majenko Uh cuz I am using my NodeMCU and I have a watchdog timer, I think there is the problem cuz it is always giving me a bunch of errors like feefeffe
• Majenko: Yes, but why there? Why between two pieces of code that are "either / or"? If the first ran then the second won't. If the second ran then the first won't have. There's no "between" in that scenario.
• Juraj: the yield() before the if is the yield() before the else

Answer 1

First of all do yourself a favour and listen to your IDE

This report would have more information with
 "Show verbose output during compilation"
option enabled in File -> Preferences.

and in an if else there is no in between so either let it run as a state machine especially inyour case A != B != C != other:

void subfunction(){
 if(A){
 // code to run
 return; 
 }
 yield(); 
 if(B){
 // code to run
 return; 
 }
 yield();
 if(C){
 // code to run
 return; 
 }
 else{} // to catch if not A or B or C
 yield();
}

or implement switch case (Pseudo code)

 switch(fromClient){
 case "LR":
 //code to run
 yield();
 break;
 case "RR":
 //code to run
 yield();
 break;
 default:
 //code to run
 yield();
 break;
 }

Id else chains are prone to errors as in your case its A != B != C != other

• Ted Lu: Thank you! But again I am at home, I'll test it tmr in my lab, thank you again!
• Juraj: why not yield() after the switch?
• Codebreaker007: I just copied his"use case" but you are right he could even do it before the cases and in the case (depends on his WD timer