please help for this function

[Saeid Reza Bahman Abadi]

h write this function

string triger()
 {
   if(iClose(Symbol(),timeframe,1)>iOpen(Symbol(),timeframe,1))
      {
         if((iClose(Symbol(),timeframe,1)-iOpen(Symbol(),timeframe,1))>(iHigh(Symbol(),timeframe,1)-iClose(Symbol(),timeframe,1)))
            return("buy");  
      }
   if(iClose(Symbol(),timeframe,1)<iOpen(Symbol(),timeframe,1)) 
     {
         if((iOpen(Symbol(),timeframe,1)-iClose(Symbol(),timeframe,1))>(iClose(Symbol(),timeframe,1)-iLow(Symbol(),timeframe,1)))
            return("sell");
     } 
   else return ("No signal"); 
 } 

but this error

'}' - not all control paths return a value

[William Roeder]

1. string triger()
    {
      if(…
      if(…
      else return ("No signal"); 
   
   What do you return here when all if's and else's are done?
    } 

2. An if(condition) statementA else StatementB; does A or does B and then the statement(s) after. If A ends in a return, then drop the else, B becomes the statement(s) after. If B ends in a return, reverse the condition and statements.
   

[Saeid Reza Bahman Abadi]

William Roeder:

2. An if(condition) statementA else StatementB; does A or does B and then the statement(s) after. If A ends in a return, then drop the else, B becomes the statement(s) after. If B ends in a return, reverse the condition and statements.
   

thank,s