stackoverflow - how to find the last item of a field and compute a running sum?

[Dean D. Babic]

Hi all, 

question from here:

https://stackoverflow.com/questions/78983991/jam-py-how-to-find-the-last-item-of-a-field-and-compute-a-running-sum

I initially misunderstood the question so answered with this:

Add this into your form (jam.py v7):

function on_before_post(item) {
    if (item.is_new()) {
        let copy = item.copy();
            copy.open();
            if (copy.rec_count ===0) {
                item.tach_in.value = 1;
            }   else {
                item.tach_in.value = item.tach_out.value;
            }
    }
}

However, I think the user would like to see the last entry on the form when creating a new record. 

So, I think we need the last value of the tach_out :

function on_edit_form_shown(item) {
    if (item.is_new()) {
        let copy = item.copy();
            copy.open();
            if (copy.rec_count === 0) {
                item.tach_in.value = 1 ;

            }   else {
                    let copy = task.flight.copy();
                    copy.open({fields: ['tach_out']});
                    copy.last();
                    item.tach_in.value = copy.tach_out.value;

            }
    }    
    if (item.tach_out.value) {
        item.total.value = item.tach_out.value - item.tach_in.value;
    } else {
        item.total.value = 0;
    }

}

When the user creates a new record, the tach_in will be automatically populated.

I think this is similar to this questions:

https://groups.google.com/g/jam-py/c/oAFTQK1yJUA/m/Wa1ngVIiCgAJ

https://groups.google.com/g/jam-py/c/VbG9kIqP95o/m/e66YzsGtCgAJ


Cheers