Using value from previous entry within a repeater

Wappler General How To
#1

What is the best way to include a value from a previous entry within a repeater?

I have a repeater that pulls a list of entries from a DB which include a DATETIME.

Per entry I want to calculate the time difference with the previous entry (* in code)

Can this be done within the repeater? Or should I recall the SC and pull the previous entry using index etc.?

This is my code:

        <div dmx-repeat:repeatlog="get_log.data.get_log.where('userid', userselection.value, '==')">
            <div class="d-flex flex-column mb-2 bg-secondary p-1">
                <div class="d-flex p-0 m-0 justify-content-between">
                    <p class="m-0 pt-0 pb-0 ps-0 pe-4">userid: {{userid}}</p>
                    <p class="text-light m-0">entry time: {{time}}</p>
                    <p class="text-light m-0">time since last entry: {{time}} * </p>
                </div>
                <p class="text-light m-0 p-0">action: {{action}}</p>
            </div>
        </div>
#2

I would do this in a DB view that you query or a repeat server-side. Deliver the time difference to the client as a value in each of the entries in the array

2 Likes
#3

Yes, I would agree… an app with Wappler is waaaaay faster if you use database views to deliver all the info you need and use the front end just to display it!

1 Like
#4

Thanks both, that makes sense. I am still struggling a bit with the server side repeat. This is what I have so far, suggestions where I go wrong?

Screenshot 2023-03-12 at 17.51.21
Screenshot 2023-03-12 at 17.51.21742Ă—412 28 KB

(the condition is based on security provider (which I took out in this screen shot))

#5

Not exactly sure what your desired result is but I can tell you what you’ve done:

Your condition says, only do this for the logged in user if their primary id is 1…so only one possible user.

You are then doing a query of your database and then attempting to repeat only the first row. I’m assuming you actually want to repeat get_log instead as it will be an array of values. Once you do that you’ll be able to select the value you are looking for inside the repeat.

#6

Thanks for your comment @mebeingken

The condition is there so only the admin (user 1) can engage with the server connect (extra security step) – its not the point here, should have taken it out for this example.

What I want to achieve is as described in my initial post:

  1. I have a repeater that pulls a list of entries from a DB which include a DATETIME.

  2. Per entry I want to calculate the time difference with the previous entry.

This is very easy to do in JS with a FOR loop etc.
But wanted to do this purely in Wappler, and in the server-side (as kindly suggested by @bpj and @Antony).

They made it sound easy ;), but I can’t seem to get the logic of the repeater and how I can call back a previous entry.

I am a bit lost here… so any suggestions (or existing tutorials that deal with similar issues) very welcome!

#7

Hey @ant… (Great name!)
I do this kinda thing in a server action using a repeat and a session variable to store the time from then previous loop… I hope that helps!

#8

Thanks, you too @Antony :wink:

Make sense, but could you clarify what do you mean by “previous loop” ?

#9

Sure! Something like this…

create $_SESSION s_last_datetime;
s_last_datetime = '';
repeat on your data
   compare s_last_date_time with this_datetime
      Do what you need to do;
   s_last_datetime = this_datetime;

The session variable value is global so will be retained for the next run around the loop.

Hope that makes sense!

Antony.