Android Question Do while/until with test at the end of the loop?

wimpie3 · Wednesday at 1:50 PM

Maybe I'm overlooking something... We currently have

B4X:

Do while condition=true
(my code)
loop

or

B4X:

Do until condition=true
(my code)
loop

But they all test the condition BEFORE beginning the loop. Is there a way to do this right before reaching the end of the loop? Like

B4X:

Do
(my code)
Until condition=true

DonManfred · Wednesday at 1:59 PM

wimpie3 said:
But they all test the condition BEFORE beginning the loop. Is there a way to do this right before reaching the end of the loop? Like

Do until condition=true (my code) loop:

Do until condition=true
(my code)
loop

will WORK if you set condition to true before the loop-line!!!

wimpie3 · Wednesday at 2:06 PM

Yes, in this particular case. But your suggestion does not work when I'm moving the pointer in a recordset with .nextrow.

I want something like this:
Do
(my code)
Until not(recordset.nextrow)

This moves the recordpointer AFTER my code has been executed.

When I do this:
Do until not(recordset.nextrow)
(my code)
Loop

the record pointer is already moved forward BEFORE it reaches my code.

teddybear · Wednesday at 2:18 PM

What does (my code) do? doesn't it handle recordsets?

walt61 · Wednesday at 3:56 PM

B4X:

    Dim goOn As Boolean = True
    Dim rs As ResultSet
    '...
    Do While GoOn
        '...
        GoOn = rs.NextRow
    Loop

ac9ts · Wednesday at 5:23 PM

Or use a for-next loop with Rs.RowCount?

William Lancee · Wednesday at 9:17 PM

This puts the condition at the end of the loop.

B4X:

Do while True
    (my code)
    If condition = True then exit
Loop

DonManfred · Thursday at 5:35 AM

ac9ts said:
Or use a for-next loop with Rs.RowCount?

You are confusing Resultset and Cursor?
Resultset has no methods to access a spezific row and also no rs.RowCount

These are only available in Cursor.

wimpie3 · Thursday at 10:49 AM

William Lancee said:
This puts the condition at the end of the loop.

B4X:

Do while True (my code) If condition = True then exit Loop

Yes this is the solution, although it would have been cool to have a while/until at the end of the loop in b4a's syntax. It exists in VB.

DonManfred · Thursday at 2:28 PM

wimpie3 said:
It exists in VB.

- B4X is not VB and also not related to VB.

Didier99 · 2025-11-03T13:55:17+0000

DonManfred said:
- B4X is not VB and also not related to VB.

But a large appeal of B4X (and used a lot in advertisements) is that the syntax is familiar to VB users. From the B4X home page:

My very first project in B4X was the conversion of a large VB project that went so quickly and so well I could not believe it, precisely because I was able to reuse a lot of existing code. That original code was written under vb6.0 (1998) and it's still there, 30 years later, some functions are untouched.
So when we (former VB users, now B4X users) come across something that sounds like it should be there, we have to say something

Edit: My code started with QuickBasic 4.5, which predates VB 6.0. QB4.5 was released in 1985, 40 years ago

Didier99 · 2025-11-03T13:57:49+0000

William Lancee said:
This puts the condition at the end of the loop.

B4X:

Do while True (my code) If condition = True then exit Loop

That is the cleanest way. Thank you

emexes · 2025-11-03T14:51:08+0000

Didier99 said:
That is the cleanest way. Thank you

That is the second-cleanest way. Cleaner is:

B4X:

Do While True
    (my code)
    If condition Then Exit
Loop

aeric · 2025-11-04T12:40:21+0000

The third way

B4X:

Dim b As Boolean
Do Until b
    YourCode
    b = Not(rs.NextRow)
Loop

ilan · 2025-11-04T13:01:22+0000

DonManfred said:
Do until condition=true (my code) loop:

Do until condition=true (my code) loop

will WORK if you set condition to true before the loop-line!!!

i think you meant "Do while" will work if you set condition to true before the loop-line!!! (and condition should change to false in the loop to exit it)

Android Question Do while/until with test at the end of the loop?

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