Candles And Series

Use this skill when loading or processing candles in MQL5 with MqlRates[], CopyRates, CopyOpen, CopyHigh, CopyLow, CopyClose, or similar functions.

Rule

When the logic depends on candle 0 being the most recent candle, always call:

ArraySetAsSeries(array, true);

Apply this before reading the array contents.

In this workspace, the default expectation for candle-processing logic is:

• index 0: most recent candle
• index 1: previous candle
• index 2: older candle

Example

MqlRates rates[];
ArraySetAsSeries(rates, true);

int copied = CopyRates(_Symbol, _Period, 0, 3, rates);
if(copied < 3)
   return false;

double current_open = rates[0].open;
double previous_high = rates[1].high;
double older_low = rates[2].low;

Validation

Before trusting candle logic, verify these points:

1. ArraySetAsSeries(..., true) is applied when the code expects candle 0 to be the latest.
2. CopyRates(...) loads only the number of candles actually needed for the pattern.
3. The code does not mix series-style indexing with chronological indexing by mistake.
4. Conditions that refer to candle 1, 2, or 3 are mapped explicitly to the intended indices.

Closed Candles

For patterns that must be built only from closed candles, do not use CopyRates(..., 0, ...) if the current forming candle must be excluded.

In those cases, start from 1, so rates[0] represents the last closed candle.

Recalculation Vs Entry

Separate these two responsibilities explicitly:

• when the pattern is recalculated
• when entry conditions are evaluated

If the pattern depends on closed candles, it can be recalculated on a new bar. If the entry depends on price crossing a level, that condition may need to be checked on every tick.

Candle Numbering

When a pattern depends on candle numbering, the convention must be written explicitly. It is not enough to say ArraySetAsSeries(..., true).

Also state what each index means in that context, for example:

• rates[0] = last closed candle when using CopyRates(..., 1, ...)
• rates[1] = previous closed candle
• rates[2] = third closed candle back

Pattern Debugging

When there is doubt about a candle-pattern calculation, create a separate EA test.

That EA should print times, OHLC values, indices, and pattern results so the calculation can be validated without mixing it with trading logic.

Function Ownership

If a class or function is responsible for calculating a pattern, it should also load the candles inside that same function.

Do not split that responsibility between the EA and the class, because that can make each place use a different window, a different shift, or a different array orientation.