StartScreen with variable control

[Lars1990]

Hi all,

With the new App.StartScreen funtionallity my method to dynamically navigate to a screen no longer works in the way I programmed it in the App.OnStart. Anyone who has ideas how to do something similar using App.StartScreen? The problem is Global Variables are not allowed, and I also think it is not possible to creat a collection in the App.StartScreen.

Kind regards,

Lars

//Retrieve go to screen from link in email
Set(varItem,Param("subEntityId"));
Set(varScreen,Left(varItem,3));

//Create collection of screens 
ClearCollect(screenIndex,
{Name:"100",Screen:'100StartDelistingScreen'},
{Name:"101",Screen:'101FillExpectedRemainingSalesScreen'},
{Name:"102",Screen:'102DetermainExpectedRemainingStocks'});

//Navigate to screen
If(
    IsBlank(varScreen),
    Navigate('900HomeScreen'),
        Navigate(
            LookUp(
                screenIndex,
                Name = varAction
            ).Screen,
            ScreenTransition.Fade
        )
    )
);

[RandyHayes]

@Lars1990 

StartScreen is a property, not an action, so you cannot put behavioral functions in it...it just defines the screen to start on.

Your OnStart action would be:

//Retrieve go to screen from link in email
Set(varScreen,Left(Param("subEntityId"),3));

//Create table of screens 
Set(screenIndex,
   Table(
      {Name:"100",Screen:'100StartDelistingScreen'},
      {Name:"101",Screen:'101FillExpectedRemainingSalesScreen'},
      {Name:"102",Screen:'102DetermainExpectedRemainingStocks'}
   )
)

There is no need to double define a variable to hold the Param passed...it is always available in your app.  Also, a collection for the ScreenIndex is a bit overkill as you are not needing an in-memory database (add/remove/edit) for the table of records for your screens...so a variable will be more effective.

Your StartScreen property would be:

//Provide screen
Coalesce(LookUp(screenIndex, Name=varAction, Screen), '900HomeScreen')

Now, I left the varAction in your formula because you did not provide a definition for it, nor a link to the Param.  So, adjust accordingly.   My guess is that it should be varScreen and not varAction, but I leave that to you to determine.

I hope this is helpful for you.

[Lars1990]

Hi @RandyHayes,

Thanks for the help! However it is not possible to pas a global variable in the StartScreen. I am now trying it differently due to your comments about no need to double define a variable to hold the Param passed and a collection for the ScreenIndex is a bit overkill.

What I did is adding which screen to navigate to with which action. So if:

Left(Param("subEntityId"),3));

=101 then navigate to screen 101FillExpectedRemainingSalesScreen' since:

Table: Actions

And then I changed the StartScreen to this:

Coalesce(LookUp(Actions, ActionID=Left(Param("subEntityId"),3),ActionScreen), '900HomeScreen')

Unfortunatly it still does not work because it expects a control value. Any how to make it understand that it is a control type?

KR,

Lars

[RandyHayes · Accepted solution]

@Lars1990 

Ah yes, sorry about that - I rarely use the StartScreen property, so forgot it doesn't like variables.

Kind of blows the whole concept!!

Oddly enough, the StartScreen property will allow collections (which really makes no sense based on it not liking a variable - they are the same thing in a way!)

So, you CAN change your OnStart to this:

//Create table of screens 
ClearCollect(screenIndex,   
      {Name:"100",Screen:'100StartDelistingScreen'},
      {Name:"101",Screen:'101FillExpectedRemainingSalesScreen'},
      {Name:"102",Screen:'102DetermainExpectedRemainingStocks'}   
)

Then your StartScreen can be as it was suggested before (slightly modified):

//Provide screen
Coalesce(LookUp(screenIndex, Name=Left(Param("subEntityId"),3), Screen), '900HomeScreen')

NOW, you appear to have put this into a table called Actions and then are doing a lookup on that.  You cannot store a control name as text and use it!  This is the error you are seeing.  PowerApps does not let you define a parameter where it expects a control as text.  

So, you would either have to change to the above, or put a Switch statement in to translate the string value to a control value....more work than it is worth in my opinion.  

With the above formula, the collection will act as the database and the names of the screens will be actual controls...not text.

[Lars1990]

Hi @RandyHayes ,

Thanks! I also got it to work using this method. But having a collection will be better since I use it in more places then only at StartScreen.

With({locvarAction: Left(Param("subEntityId"),3)}, 
If(IsBlank(locvarAction),
'900HomeScreen',
locvarAction="101", '101ApproveGate1Template',
locvarAction="102", '199StandardActionScreen',
locvarAction="103", '199StandardActionScreen',
locvarAction="104", '199StandardActionScreen',
locvarAction="105", '199StandardActionScreen',
locvarAction="106", '199StandardActionScreen',
locvarAction="107", '199StandardActionScreen',
locvarAction="108", '199StandardActionScreen',
locvarAction="109", '199StandardActionScreen',
locvarAction="110", '199StandardActionScreen',
locvarAction="111", '199StandardActionScreen'

))

[RandyHayes]

@Lars1990 

Usually you would not want to put a static table of records into a Collection as it is not needed and a variable (which is global to the app as well) is fine.  HOWEVER, in this particular case, for some reason they have not supported global variables in the StartScreen property (yet), so the collection is the only choice.