Confused about OnTick vs OnNewCandle best practices

[booboothefool]

I currently coded an EA all in the OnTick function. Similar to this template:

void OnTick() {
  bool longSignal = check MACD cross up;
  bool shortSignal = check MACD cross down;

  if (OrdersTotal() > 0) {
    if (shortSignal)
      OrderClose(Buy orders);
    if (longSignal)
      OrderClose(Sell orders);
  }

  if (OrdersTotal() == 0) {
    if (longSignal)
      OrderSend(Buy);
    if (shortSignal)
      OrderSend(Sell);
  }
}

I noticed this works how I want and expect during backtesting. 

When forward testing live though, I am seeing it do things like spam multiple orders within seconds, even though it is on the Daily chart. 

After researching this phenomenon, I found some information about how this might be related to ticks vs candles. I was wondering if someone could tell me more about this idea and point me in the right direction and provide some guidance on what should be done OnTick vs. OnNewCandle? I already noticed that probably OrderSend() should be done only on new candles or else it will spam orders like I saw. Should things like signals also be checked only on new candles?

Also, during backtesting I usually pick the "on Open Prices" option because the "on Ticks" option takes much longer. Is this the reason why I didn't notice any issues during backtesting? When using this testing mode, does it just automatically take OnTick() and only run it for new candles?

Please advise. Thank you!

[Yuan Gao]

please check your long or short signal carefully, they must be mutually exclusive.

anyway, if you need to run some functions once a candle, you can use Volume() function to check the volume of the latest candle.

if(Volume[0]==1) {}   //run some functions once when a new candle appeared

[William Roeder]

For a new bar test, Bars is unreliable (a refresh/reconnect can change number of bars on chart,) volume is unreliable (miss ticks,) Price is unreliable (duplicate prices and The == operand. - MQL4 programming forum.) Always use time.
          New candle - MQL4 programming forum #3 2014.04.04

I disagree with making a new bar function, because it can only be called once per tick. A variable can be tested multiple times.

[JC]

jackycode:

anyway, if you need to run some functions once a candle, you can use Volume() function to check the volume of the latest candle.

I really wouldn't use Volume[0] to test for new bars. There have been repeated real-life tests saying that it's not fully reliable.

For example: https://www.mql5.com/en/forum/125906#comment_3272369 and the topics it links to. While those discussions are over 10 years old, I wouldn't assume that it's become any more reliable during that time.

[Alekss Zukovskis]

Yuan Gao #:

please check your long or short signal carefully, they must be mutually exclusive.

anyway, if you need to run some functions once a candle, you can use Volume() function to check the volume of the latest candle.

Are you a genius? it took me 5 lines to do what you could in 1 sentence.