SaveData - ClearCollect or Collect?

[Anonymous]

Just wondering if the SaveData function acts like ClearCollect() or Collect() when saving to a device.

I'm wanting to know if I need to clear a saved / cached collection first before re-saving any changes I've made to the related in-App collection.

Thanks

[WarrenBelz · Accepted solution]

Hi @Anonymous ,

SaveData acts like ClearCollect and overwrites what is there. Here are some docs on it.

[Anonymous]

@WarrenBelz 

Thank you for that link, I have been referring to it in my research but I can't see where it says it acts like ClearCollect / Collect? Are you saying this from personal use or is there some other documentation I could reference? 

This link kind of infers that a new cached file is created but I feel it's unclear. My offline process would be (after originally saving data to a device):

1. App.OnStart = LoadData(inAppCollection, "tempCache", true)

2. Add/Edit/Remove from inAppCollection as required.

3. SaveData(inAppCollection, "tempCache")

I'm wanting "tempCache" to get overwritten at Step 3 ie ClearCollect() and not added to.

I was thinking if the SaveData() functionality was unclear then I would need to add Step 1.1 to the above, ie

  1.1 ClearCollect(colTempCache, inAppCollection) ; Clear(colTempCache); SaveData(colTempCache, "tempCache")

This would ensure "tempCache" was empty and maintained the same schema, but I don't really want to do this if it isn't 100% required.

Actually, after writing all of the above, I might just go and test it myself 🙂 

[WarrenBelz]

Hi @Anonymous ,

Please disregard this I think - I was having trouble finding my code.

It seems from it (I wrote it a long time ago) that it adds to the data as I have another mechanism to delete items from the collection.

[WarrenBelz]

I will get you my code when I get back to a PC. It is scattered throughout a large app and as you know there is no code search function If this was VB you could find it in a minutes. I am still not completely sure.

[Anonymous · Accepted solution]

@WarrenBelz 

No worries mate. From my testing it appears that it acts as ClearCollect(), as you stated. I think I covered all probable use states in my testing but I'd be keen to run some double checks with your code.

I'll mark your answer as a solution, thanks again.

[WarrenBelz]

HI @Anonymous ,

Now I have found it all and I was correct with my "first instinct" - SaveData does replace the device data.

Here is the whole process I use for offline photos.

The bit not here is that I use Connection.Conected test on every screen and if not online, all other screens other than the offline photo screen have only a button in the middle to navigate to the offline screen. So from the start

At App OnStart - it loads data from olPhotos storage on device into Collection OLPhoto. The true parameter tells it to ignore the command if the phone currently has not had the storage configured.

LoadData(
   OLPhoto,
   "olPhotos",
   true
)

Now the camera takes a picture and sends it to collection OLSample so it can be reviewed in the Image control

ClearCollect(
   OLSample,
   CameraScreenO.Photo
)

Now when the user accepts this picture - it is collected from camera screen and ADDED to collection OLPhoto, then this is saved to the device collection to device storage olPhotos REPLACING data currently stored

Collect(
   OLPhoto,
   {
      sPhoto:ImageDisplayO.Image,
      sNotes:PhotoNotesO.Text,
      sDate:Text(Now(),DateTimeFormat.ShortDateTime24,"en-GB")
   }
);
SaveData(
   OLPhoto,
   "olPhotos"
)

Now to delete an item - first bit displays a big red pop-up with the picture image for the user to confirm they want to delete it.

Set(vDelete,true);
Set(vDelItem,ThisItem)

Then if the user selects the confirmation, REMOVES the item from the collection OLPhoto and then writes to the device REPLACING the data olPhotos with the updated collection. Then the pop-up disappears.

Remove(
   OLPhoto,
   vDelItem
);
SaveData(
   OLPhoto,
   "olPhotos"
)
Set(vDelete,false)

It all has worked fine for some time and we intentionally made the users clear them one at a time when they came back online and uploaded them (using the normal screen, but collecting from OLPhoto instead of the camera).

I hope this is useful to you.

[Anonymous]

@WarrenBelz 

Many thanks for your reply, it's very helpful. There are some great insights into usage that I can draw from.

Thanks for taking the time to write out this reply, I greatly appreciate it.

Just out of curiosity, as your users are saving images on their phones (?) with this app, have they ever encountered storage issues? My app/s won't be saving images - yet - but I'd be interested to know if storage ever becomes an issue.

cheers 

[WarrenBelz]

Hi @Anonymous ,

The great thing about PowerApps camera control images is that they are very small (under 100k). The users also know how to clear them out and generally do so when they come back on line and upload them, otherwise they see them again every time they go offline.

[Anonymous]

Thanks @WarrenBelz , once again, great insights