Arrow: Draw Only Once / doOnce

[Tradexxx]

hi!
try to build an indicator and therefore i'm using the strategy builder at first.
the arrows i want to be drawn are drawn, but not only once, rather each time the signal is valid.
as i just want to see the first valid signal being signed with an arrow, i tried what i found in forum here:

https://ninjatrader.com/support/forum/forum/ninjatrader-7/indicator-development-aa/103628-draw-only-once

but, i assume because it's NT7, it's not working for NT8...

how do i have to do that in NT8?
btw: it's not the case that the describe "doOnce" is not working in a strategy, but in an indicaotr, or?
thank you very much!

[NinjaTrader_ChrisL]

Hi Tradexxx, thanks for your post.

It's happening because the Tag string is not unique. Append the CurrentBar value. In the drawing tool>Tag>Set>Add>Set>Misc>select Current Bar and click OK.

This will append the CurrentBar value to the Tag string so that each tag is unique.

Please let me know if I can assist any further.

[Tradexxx]

hi chris,
thank you for your answer.

the CurrentBar value is set.
but the first error appears when i try to build : "private bool doOnce = true;"

the indicator i'm using is an oscillator. but that shouldn't be a problem, or?

attached you'll find a quick testcross strategy, drawing an arrow at each cross.
when i try to add the expression "private bool doOnce = true;" the same error appears....

thank you for your assistance

[NinjaTrader_ChrisL]

Hi Tradexxx, thanks for your reply.

So the issue is your getting multiple signals on a single bar but only one draw object is showing up (the last one)? You would need to append the Price onto the Tag to make the intra-bar draw objects unique in this case. The post you linked is making it such that only one draw object is made per bar.

I look forward to hearing from you.

[Tradexxx]

hi chris,
thanks for your replay.

the point is i'm getting one arrow per bar.
after the first arrow appears(the one i'd like to see), each following candle is also being painted with an arrow, as long as the condition 1 is valid.

therefore i'd like to use "doOnce" to take the other arrows out, as long as another condition is going to end condition 1.

pls. see attached screen.

[Tradexxx]

activation of line 58 in the file above, shows the error, i'm talking about

[NinjaTrader_ChrisL]

Hi Tradexxx, thanks for your reply.

If you need to reset that boolean reset it based on the CurrentBar.

int PrevCurrentBar = 0;

OnBarUpdate()
{
    if(PrevCurrentBar != CurrentBar)
    {
        PrevCurrentBar = CurrentBar
        doOnce = false
    }
}

[Tradexxx]

hi chris,
unfortunately, it's not working....
errors appear at
- PrevCurrentBar = CurrentBar AND
- doOnce = false;

[NinjaTrader_ChrisL]

Hi Tradexxx, thanks for your reply.

Could you post what you have so far?

[Tradexxx]

hi chris!
first of all: thank you for your assistance!
perhaps the selected and posted example wasn't the best, because it's based on a "crossabove.." event (happening only once), while the strategy i'm using has the condition to be true unless it's invalid (causing arrows are painted again and again..)
so i have changed the example above from 'crossabove' to 'greater' to see better what's happening.

pls. see attached file.
i have added your suggestions, but it's not working like expected.

[NinjaTrader_Jim]

Hello Tradexxx,

Please consider the following:

private EMA EMA1;
private EMA EMA2;
private bool doOnce;

protected override void OnStateChange()
{
    if (State == State.SetDefaults)
    {
        Description                                    = @"Enter the description for your new custom Strategy here.";
        Name                                        = "Testcross2";
        Calculate                                    = Calculate.OnBarClose;                        
    }
    else if (State == State.DataLoaded)
    {                
        EMA1                = EMA(Close, 14);
        EMA2                = EMA(Close, 21);
        doOnce                = false;
    }
}

protected override void OnBarUpdate()            
{
    if (EMA1[0] > EMA2[0] && !doOnce)
    {
        Draw.ArrowUp(this, @"Testcross2 Arrow up_1 " + Convert.ToString(CurrentBars[0]), false, 0, (Low[0] + (-3 * TickSize)) , Brushes.Lime);
        doOnce = true;
    }
    else if (EMA1[0] <= EMA2[0])
    {
        doOnce = false;
    }
}

1. doOnce is false
2. If doOnce is false and condition is met, Draw object and set doOnce to true. The condition will no longer become true because doOnce is true, and we are checking if it is false.
3. On a reversal condition, we set doOnce back to false so the logic above can become true again.

We look forward to assisting.

[Tradexxx]

hi jim,
thank you very much for the explanation!!