Experts: New Candle or Bar formation. - page 2

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Maxim Kuznetsov # :

1. Improperly initialized previous_time, causing false alarms immediately upon code startup.

2. Expensive access to iTime at each tick.

3. Not all ticks form a bar (in rare cases, a tick can occur on an off day and is not a transaction, but just some internal server procedure).

The work of the code is to detect new candle formation which can only by written inside an Ontick or OnTimer function
 

You can't know when a candle closes. Only when a new tick arrives that starts a new bar is the old bar closed, and that tick could arrive almost at the end of a bar's duration.

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.
          MT4: New candle - MQL4 programming forum #3 (2014)
          MT5: Accessing variables - MQL4 programming forum #3 (2022)

I disagree with making a new bar function, because it can only be called once per tick (second call returns false). A variable can be tested multiple times.
          Running EA once at the start of each bar - MQL4 programming forum (2011)

 static datetime curDT=0; datetime preDT=curDT; curDT=iTime(_Symbol,_Period,0);
 if(curDT != preDT){ … }
 
William Roeder #:

I disagree with creating a new bar function, because it can only be called once per tick (the second call returns false). A variable can be checked several times.

I managed to make a generic function IsNewBar(symbol, timeframe), which works correctly within one EA for different combinations of symbol and timeframe, and can be called multiple times within the processing of one tick, returning the same thing the second time (and subsequent times) as the first time.

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