Default Value is not working well with Variables

[johnjohn123]

I a Number field named "ScoreGreenPoint" + a Button named "+Green".. the scenario is that when i click on the "+Green" button the ScoreGreenPoint should get incremented by 1.

for the ScoreGreenPoint i set the default value to be

Coalesce(Parent.Default,varGreenCount)

and the "+Green" to be :-

Set(varGreenCount,varGreenCount+1)

now when i create a new item the +Green button will increment the ScoreGreenPoint correctly, but if we edit an item which already have values inside the ScoreGreenPoint, the +Green will not increment the ScoreGreenPoint .. any advice?

[johnjohn123]

@RandyHayes  to be honest i did not get your point? and how it relate to the issue i am facing? am i missing something?

[RandyHayes]

@johnjohn123 

You were concerned with the formula "running" once or again and again.  I was addressing that point.  They don't run, they evaluate.  

So, if your varGreenCount is blank, then the Parent.Default value is use, if it is blank, then 0 is used.

Once you set a value to varGreenCount, it will then have a value and the formula will re-evaluate immediately to show the value of varGreenCount.

[johnjohn123]

@RandyHayesok this makes sense to me now... so the formula  Coalesce(varGreenCount, Parent.Default) will check the sequence again and again?similar to excel if you have a cell which depend on another cell, then changing the second cell will have the cell which depend on it.. is this correct?

[RandyHayes · Accepted solution]

@johnjohn123 

Yes, that is correct.

Back to your formula (and let's go with Coalesce(varGreenCount, Parent.Default, 0) ), if you are editing a record with 5 in the underlying datafield and varGreenCount is blank, then you will see 5 in the "cell".  If the record is new, then you will see 0.

If you then increment varGreenCount (with the formula previously provided) to the point where it has a value of, let's say 10, then the rest of the Coalesce is not important because it has a value and the "cell" will evaluate to 10.  And that is what you will see.

So, if you had a button on your screen that had a OnSelect action of : Set(varGreenCount, Blank())

And your Underlying record had 5 in it, then when you press that button, the "cell" will go back to 5. 

It's all very "Excellish"

[johnjohn123]

@RandyHayesok got it now..thanks so Coalesce in a way or another works simialr to formuals insdie excel

[RandyHayes · Accepted solution]

@johnjohn123 

Well no, not just Coalesce - EVERYTHING in PowerApps!  Everything is evaluated in real time in PowerApps (except again, behavioral actions which on evaluate when their trigger occurs).

Every control property on every screen is evaluated in Real-time in PowerApps all the time.

Things that are not evaluated and thus YOU must maintain on your own are, variables and collections (which is a good reason to avoid them UNLESS you need a static snapshot of something)  Let the magical power of PowerApps do all the evaluation work for you all the time.  In the case of variables, It's like in Excel, you wouldn't try to set a variable to the value of a cell so that you can use it in the formula of another cell...you would just reference that cell in your formula.  Same deal in PowerApps.

As for Coalesce:  Coalesce is just one of a large list of functions in PowerApps that can be used in any formula for evaluation or action.

And by the way, for understanding Coalesce more,  these two formulas are equivalent:

If(!IsBlank(varGreenCount), varGreenCount, If(!IsBlank(Parent.Default), Parent.Default, 0))

Coalesce(varGreenCount, Parent.Default, 0)

The Coalesce is a lot less formula to write and much easier to read.