Gallery Template fill based on value in 2nd gallery

[JR-BejeweledOne]

I need to set the template fill of a gallery if the date exists in a 2nd gallery.

Gallery1 - Dates

   Title - Number

   Subtitle - Text

   Label7 - Number

Gallery2 - (Vertical Blank Flexible Height) Items

   LabelDate - Text

   LabelHoliday - Text

If Gallery1 Subtitle (text date) is in Gallery2 LabelDate (any item), then I need the template fill to be a color other than white.

In trying to do this, the only comparison option I have in Gallery1 is ThisItem.Value.  I can't select one of the controls inside the gallery item.   ThisItem.Value evaluates to a number but it won't allow me to use the = operator to compare to the number field inside gallery2.

Would appreciate suggestions and recommendations.

[Rivius]

I'm curious why you seem so biased against a collection in this case.  I use collections frequently when handling most kinds of data manipulation and to avoid extra calls to the datasource so mobile users don't get hung up.

[JR-BejeweledOne]

Thank you.  That works perfectly

[JR-BejeweledOne]

Ok, that worked and it didn't work.

Gallery2 is Filtered.  CountRows shows 13 rows.  In that 13 rows, there are 2 January dates, but as you can see below, more than 2 items have a different bg color.   Only the 1st and the 6th should have a different bg color.

[RandyHayes]

@Rivius 

A collection is a duplicate of data based on a duplicate of data (the datasource) based on a duplicate of data (the session table) based on a duplicate of data (the real data).

Collections are just like a variable that you have to maintain in your app through behavioral actions. 

Collections ONLY provide the means to easily add or remove a row in its table.  AND, they bring along this overhead to your app even if you don't use it.

I could go on as to why NOT to use them.

However...I have no bias against them.  They have their place.  Collections are necessary for when you need an in-memory database that you can add or remove rows from - such as an offline mobile app where you need that, or when you want to easily add/remove like in an editable table.  If the data you are gathering is static, it is best to assign to a variable instead.  If not, then a collection.

Collections are overused by most because it provides a comfort concept to a development array.  In order to use them, you must do so in Behavioral actions.  Behavioral actions are again, a comfort concept to a development platform.  PowerApps is not a development platform.  It is a platform that is built around Excel.  It is reference based, not behavioral based.  What makes PowerApps great is that it IS Excel like AND that it offers some ways to do some things that you could not do easily in Excel - like behaviors.  However, developers coming into the PowerApps world discard the Excel like nature of PowerApps and instead look to do everything in behaviors.  This makes for a over-complex, difficult to design and maintain and adds tremendous amounts of extra work that is completely unnecessary.  

So, in the case of @JR-BejeweledOne - there is ALREADY a table to reference which is the gallery.  It is a table, it has an AllItems property that exposes the whole table and all of the already done controls.  So, trying to base that on a collection instead and referencing the collection is just MORE unnecessary work because the data is already there!

As for "trips" to the datasource.  You actually kill performance in your apps with collections.  It is incorrect that PowerApps is making trips back to your datasource all the time when you want a value.  The session table and datasource in the app "hold" their data once requested.  If you first get record 1 in your app, the app will go to the datasource (real) and get it.  If you need it again, it already has it.  When you then want record 2, it will get it and then have it.  When you put a collection in to gather ALL of the records, you then force PowerApps to gather all of the data as a snapshot.  The trouble comes that most will then update a record in the datasource in the app and then refresh the datasource and then recollect the information again...this is a horrible performance kill.  Point is, the datasource is already a table of information to use - use it!  People tend to use collections to solve a problem they don't have.

I only dissuade collections in most posts because of much of the above and that they are simply overused and add overhead.  Personally, I want people to have a pleasant experience designing Apps in PowerApps.  If they have to think "programmer", they will struggle or fail.  If they look at their app as a big spreadsheet where they can reference and use data already available, they will be successful.

Trust me, I started out using collections for everything I did.  I struggled and always thought that a collection was the answer, but then I had to constantly maintain them.  Once I dropped the "developer" mind and went with the Excel concept, productivity of Apps increased 1000%

Also, once I discovered "dynamic variables", there was never a need for collections again except for the offline app and places where an in-memory database was desired.

I've already rattled on long enough with this, so I will not describe dynamic variables here.

I hope this is clear and helpful for you and perhaps it will shed some extra light on your approaches and increase productivity for you as well.

[Rivius]

Randy, thank you very much for taking the time to explain all of that.  This has given me some things to think on for optimizing my apps and I appreciate it truly.  Be well and have a good day!

[RandyHayes]

@Rivius 

No problem at all.  Been doing this for a long time now.  Learning the concepts allowed me to produce more apps and in much less time that worked better and users liked.  I was able to divert my focus from "how can I do this and how do I maintain all these variables and collections?" to "what cool user feature can I throw in to the app in the next 20 minutes that users will love?"

Always here to answer questions you might have!

[RandyHayes]

@JR-BejeweledOne 

So, the formula I provided is going to compare the text to text in the labels.  What are your Text properties on the labels?  Did I assume correctly that Subtitle was the label with the actual date in it?  What is its text property?

[JR-BejeweledOne]

I figured out what the issue is.  It has to do with the fact that it's comparing a number, due to the text property,  rather than a date, which is what I need.   I slapped a label in Gallery1, changed Title1 text value to DateAdd(varFirstDays.January, ThisItem.Value, Days) and then set the text of the label to ThisItem.Value.  As I suspected it now shows a date rather than a single number (1,2,3, etc.).  If I change Title1 back to Day(DateAdd(varFirstDays.January, ThisItem.Value, Days)) then the label shows the expected number.

Since I need the number, I will keep the subtitle (label) and set it's text value to DateAdd(varFirstDays.January, ThisItem.Value, Days) as this will show the date.

So then I should be able to compare it to the Date in Gallery2.   Currently the Date in Gallery2 is set to DateValue(ThisItem.Date) as Date is a single line of text field and the Gallery1 label field is a date value.   No errors in the formula, but no fill change either.   I am sure it's something to do with the Subtitle2.Text, but that's the only option that doesn't cause an error.

Subtitle2:

Gallery2 - Date: 

Fill:

[RandyHayes]

@JR-BejeweledOne 

You missed one key element in your formula....you are comparing a control to a text  (Date = Subtitle.Text).

Change your formula to the following:

If(LookUp(GalleryHolidays.AllItems, Date.Text = Subtitle2.Text, true), Style.DayBG, White)

[JR-BejeweledOne]

It really doesn't like that.  I think it's because Subtitle2.Text is actually a Date value and not a text value.   If I just do '"Date.". (without the quotes)  It doesn't give me any options at all.