透過 handle 使用內建指標

//+------------------------------------------------------------------+
//| Lesson 14 - Indicator handles: iMA + iATR                        |
//| Read-only: this EA prints values, it does not trade.             |
//+------------------------------------------------------------------+
#property copyright "Strategist Academy"
#property version   "1.00"
#property strict

input int MAPeriod  = 20;
input int ATRPeriod = 14;

int maHandle  = INVALID_HANDLE;
int atrHandle = INVALID_HANDLE;
datetime lastBarTime = 0;

int OnInit()
{
   maHandle  = iMA(_Symbol, _Period, MAPeriod, 0, MODE_EMA, PRICE_CLOSE);
   atrHandle = iATR(_Symbol, _Period, ATRPeriod);

   if(maHandle == INVALID_HANDLE || atrHandle == INVALID_HANDLE)
   {
      Print("Failed to create indicator handles. Error: ", GetLastError());
      return(INIT_FAILED);
   }

   Print("Handles created. MA=", maHandle, "  ATR=", atrHandle);
   return(INIT_SUCCEEDED);
}

void OnDeinit(const int reason)
{
   // Always release - a leaked handle per backtest pass will stall the tester.
   if(maHandle  != INVALID_HANDLE) IndicatorRelease(maHandle);
   if(atrHandle != INVALID_HANDLE) IndicatorRelease(atrHandle);
}

//+------------------------------------------------------------------+
//| Pull one value out of an indicator handle                        |
//+------------------------------------------------------------------+
bool ReadValue(const int handle, const int buffer, const int shift, double &out)
{
   double buf[];
   ArraySetAsSeries(buf, true);            // 0 = newest

   int need = shift + 3;
   int got  = CopyBuffer(handle, buffer, 0, need, buf);

   if(got < need)
      return false;

   double v = buf[shift];
   if(v == EMPTY_VALUE || v == 0.0)
      return false;

   out = v;
   return true;
}

void OnTick()
{
   datetime t = iTime(_Symbol, _Period, 0);
   if(t == lastBarTime) return;
   lastBarTime = t;

   // shift 1 = last CLOSED bar. shift 0 is still forming and will repaint.
   double ma  = 0.0;
   double atr = 0.0;

   if(!ReadValue(maHandle, 0, 1, ma))
   {
      Print("Could not read MA yet - not enough bars.");
      return;
   }
   if(!ReadValue(atrHandle, 0, 1, atr))
   {
      Print("Could not read ATR yet - not enough bars.");
      return;
   }

   double bid = SymbolInfoDouble(_Symbol, SYMBOL_BID);

   Print("bid=", DoubleToString(bid, _Digits),
         "  EMA(", MAPeriod, ")=", DoubleToString(ma, _Digits),
         "  ATR(", ATRPeriod, ")=", DoubleToString(atr, _Digits),
         "  ATR in points=", DoubleToString(atr / _Point, 1),
         "  price is ", (bid > ma ? "ABOVE" : "below"), " the MA");
}