How to reference a datasource without loading it (i.e. a pointer)

[Anonymous]

Hi, I am currently building an app with multiple datasources which may or may not be accessible by all users. So upon starting the app, I want to create a collection that has all of the datasources that a user can access for easy reference. I am trying to do something as follows (in pseudo code) :

However, this solution actually loads the datasource into my collection which I do not want. Is there a way to reference the datasource without actually loading it into the collection? (Or in programming terms is it possible to create a pointer for datasources?)

[jlindstrom]

Build an app launcher app that launches different apps rather than trying to do all of it in one app. All connections neede by your app need to be connected to your app and will need to be authenticated by the user

see the Microsoft healthcare emergency response app solution for a good example of this. The main app has a menu and each menu option is a different app https://powerapps.microsoft.com/en-us/blog/emergency-response-solution-a-microsoft-power-platform-so...

that way you can conditionally give access without the users having access to all of the connections 

[Anonymous]

Hi @jlindstrom ,

Thanks for your suggestion. However, it is not a viable solution for my case as there will be around 10 different data sources and different users will have access to different permutations of the data sources which will require way too many apps. Is there a workaround for this?

As for the connection requirement, I am using SharePoint lists as the datasource and the app can still launch and work normally even if the user cannot access all the lists.

[jlindstrom]

I see you are using 10 sharepoint lists which is one connection, so that solves the login issue. When I was talking about different fldatasourcrs I meant different connections

[v-siky-msft]

Hi @Anonymous ,

Could you please share more details about your scenario?

After my test, I found your solution seems feasible, it could be something logic error if it loads the datasource into my collection which I do not want, please share more information about it.

In my test, it can embed all list tables into Data Source column in collection, and take Name column as index to reference the Table when I use this code.

Clear(Coltotal);
Collect(Coltotal,{DataSource:'SP list1',Name:"SP list1"});
Collect(Coltotal,{DataSource:'SP list2',Name:"SP list2"});

Hope this helps.

Sik
 

[Anonymous]

Hi @v-siky-msft ,

Thank you for the detailed reply! Initially my first thoughts was also to do the same thing as your test. However the problem is that it loads the entire database into the collection. This is a concern because:

1. It may cause performance issues if there is a large amount of data from each source. Normally only a filtered subset of the data from each datasource is loaded.
2. The data in the collection is now a separate copy of the data from the datasource. This means that any modification to the data in this collection will not be saved into the original datasource. I have tried to get around this using the Patch function but it does not work.

 To illustrate, I will use the code you have written to load the data into a collection.

Now, I try to update the "Description" field of the last record in "SP list1" using the Patch function. This gives me the following error.

Essentially, building on your example, I want to be able to use 

in place of 'SP list1'. The reason for this is so that the user access rights for each list only needs to be checked once on the app initialization. Then, subsequently I can just refer to this collection to know which datasources the user can access rather than having to check through all the datasources again. I hope that I've explained the scenario well enough. Do let me know if there is anything I can elaborate on or if there is any alternative way to achieve what I'm trying to do here. Thanks!

[v-siky-msft]

Hi @Anonymous ,

Sorry, I still don't get what you mean and what you want to do in the App..

If the available lists are different for each user, how do you ensure that the formula can dynamically select corresponding data source?

Sik

[timl]

Hi @Anonymous 

Unfortunately, it is not possible to 'point' to a data source, or to store a pointer to a data source in a variable.

I agree that this would be a great feature and there are similar related posts that you can find in the ideas forum.

https://powerusers.microsoft.com/t5/Power-Apps-Ideas/Dynamic-Data-Source/idi-p/178095 

https://powerusers.microsoft.com/t5/Power-Apps-Ideas/Use-a-variable-to-indicate-source-for-patch/idi-p/252890 

[Anonymous]

Hi @v-siky-msft ,

On app start I will check for access to the data sources like using If functions to check for access. The IsEmpty function will throw an error if the user cannot access that list. Thus, only the accessible data sources will be added.

Then, I use my collection to as the datasource for a gallery (i.e. FilterGallery) to generate at runtime buttons that users can click to select the datasource. Note that "DRUPS3" is missing because I cannot access that datasource.

Now, when a user clicks the button, it will change the datasource of a different gallery that I am using to display the data (i.e. DisplayGallery) by simply setting the "Items" property of DisplayGallery to:

FilterGallery.Selected.DataSource

Here is the problem, the items shown this DisplayGallery is merely a copy of the original datasources. If there is any change to my original datasources, even if I refresh the connection, the DisplayGallery will not show the changes. The desired behavior is to have a reference to the datasource so that if anything changes, the DisplayGallery will also show the changes when the connection is refreshed. I apologize if it is still a little unclear.

[Anonymous]

Hi @timl ,

Thanks for letting me know. Have you had any luck using a workaround for this or something similar?