# `data.write_before_call`

Write comes before a later outside call.

Area 6, [Reads and writes](../topics/reads-and-writes.md); not declinable; the next step is usually the agent's.

No transaction is open while an outside call is out, so an action's
writes come after its last call ("Several outside calls"). The error is
at the write, naming the last call it comes before; one made through an
action it calls names that action and the call it makes:





```jadpo
use app { sheets }
use bakery/entities { PriceSheet }
use bakery/types { SheetText }
use bakery/failures { SheetNotKept }

/// Marks a supplier's price sheet checked, then keeps the sheet they sent
/// again: the write comes before the call.
action recheck_prices(
    price_sheet: PriceSheet,
    sheet_text: SheetText
) fails SheetNotKept -> PriceSheet {
    var checked: PriceSheet = PriceSheet.update(price_sheet) {
        set: {
            checked: true
        }
    }
    var sheet: File = attempt sheets.put(encoding.to_utf8(sheet_text), FileType.csv) {
        storage_full: SheetNotKept
    }
    return PriceSheet.update(checked) {
        set: {
            sheet: sheet
        }
    }
}
```

```text
error: `PriceSheet.update` writes before the call to `sheets.put`
 --> domains/bakery/actions/recheck_prices.jadpo:12:31
   |
12 |     var checked: PriceSheet = PriceSheet.update(price_sheet) {
   |                               ^^^^^^^^^^^^^^^^^ writes here
17 |     var sheet: File = attempt sheets.put(encoding.to_utf8(sheet_text), FileType.csv) {
   |                               ---------- the call it must follow
  reason: No transaction is open while an outside call is out, so an action writes only after its last call; run as written, `sheets.put` would be refused.
  next: Move `PriceSheet.update` after `sheets.put` (agent)
  rule: data.write_before_call
  help: https://jadpo.dev/docs/errors/data.write_before_call

check failed: 1 error, 5 files
```