How to use cloud_username as filter for layer?

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1

Hi all,

I would like to use @cloud_username to filter the layer that is set as geofencing layer. This way I can create a dynamic geofence. Consider a polygon layer with suburbs. A project manager can fill an attribute ‘surveyor’ with usernames and set a filter to that layer (“surveyor = @cloud_username )This layer is set as the Geofencing layer. So user 1 is assigned to suburb a, user 2 to b etc.

Now, when a user opens the project in the QFied app the Geofence is applied based on the username.

However: QGIS filter does not use variables as input. This is a feature request since 2017: Allow qgis variables in provider filter · Issue #24662 · qgis/QGIS · GitHub

Is there another way to use variables as filter?

Is there another way to prevent users from editing outside their designated ‘area’?

2

I am looking into a possible workaround:

Consider the polygon layer with suburbs. I add two new fields, surveyor and active. The field surveyor is populated by the project manager with cloud usernames: user1 for suburb a, user2 for suburb b, etc

The field active is a boolean type which has Default set as “surveyor” = @cloud_username

Then, a filter can be applied with the expression “active” = TRUE

However, this will only work when ”active” is being updated on opening the project in QField. I have not found a way for this to happen yet. I can set the field active to Apply default value on update, but I am not updating this layer as a QField user, I am only opening the project.

Is there some kind of trigger that will update the field “Active” on opening the project in QField? And then apply the filter as next step?

3

Hi! I unfortunately haven’t worked with filters so far, but you can set up expression-based permissions for a layer, which might give you the result you want.

If I remember correctly, the example below would make it so that a feature can only be edited if the @cloud_username matches the value in the field “user”, when put in “Disable attribute editing”, “Disable feature deletion”, and “Disable geometry editing”.

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4

interesting idea.

It does work when I set the ‘user’ per feature. That is however not what I am looking for, I want to set it so a user can only edit a point feature laying within a certain polygon.

I tried overlay_within(‘polygonlayer’, filter:= surveyor != @cloud_username)

Here I run into the same issue that a filter expression does not work with variables.
If I use a hardcoded value in stead of @cloud_username it does work. This unfortunately is not the solution, because it no longer is dynamic.

5

I have created a workaround. See this topic in Advanced Use and Customization: