THE NEW START FUNCTION FOR INDICATORS:
Though being dropped in a chart is the initial event that causes an indicator to run, from that point on, it is in "tick wait" mode and will not do anything more until and unless a "special event" (i.e., a new price) comes in.
It is this subsequent event that causes the function to re
calculate everything. It performs this recalculation for the new updated price, hence the new name for the
indicators start function is...
OnCalculate()
When the function finishes running, it returns a number, or
integer. So then, the datatype for the indicators start function is…
int, so that the function is coded as follows:
int On Calculate()
{
Xxxx xxxxxxx xxx xxxxxxx xxxxxx xx xxxxx;
return(rates_total);
}
In a real file, this "special event" driven OnCalculate() function looks like…
int OnCalculate
.(
..const int rates_total,
...const int prev_calculated,
...const datetime &time[],
...const doubled &open[],
...const doubled &high[],
...const doubled& &low[],
...const doubled& &close[],
...const long &tick_volume[],
...const long &volume[],
...const long &spread[] .)
{
Xxxxx xxxxx xx xxxxxx xxxx x xxxxxx;
return(rates_total);
}
Note that there is a list of constants (const) that go between the parentheses, and that they are separated by commas. (The const is a type of "access specifier" that prevents a parameter from being changeable, which is to say, it keeps it
constant—or constantly maintained at whatever it was originally set to be.)
At the end, the function returns the rates_total.
The rates_total typed inside the parentheses following "return" is the information that the indicator start function provides or delivers. It is the
integer returned on every run of the function, and is the reason OnCalculate() is of the
int data type.
