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CheckFields

function CheckFields(aFieldNames: string): string

Example​

procedure ScriptEvent(var Value: variant);
begin
  Value := DATA1.CheckFields('CustomerCode,Status,UpdatedAt');
end;

Usage​

CheckFields concatenates selected current-row field strings after comma tokenisation, without delimiters or null/type markers.

Usage notes

Use only for lightweight comparisons under a fixed schema/order/locale. Trim and validate a configuration-provided field list before calling. Do not use the result as a canonical key, secure hash or unambiguous serialization.

Side effects and errors

The method reads the current row without navigation or data mutation. Inactive/destroyed state, a missing/space-prefixed field, unsupported conversion or field event can raise. The retained builder is mutable and unsynchronised.

Additional Technical Info​

CheckFields returns a delimiter-free concatenation of AsString for selected fields in the current record. aFieldNames is a comma-separated Velox token list, not the semicolon syntax used by dataset indexes/Locate.

The example selects three required fields. It is source-reviewed and was not executed by the documentation workflow.

Signature

Tokenisation

Velox StringToToken scans characters and splits only at commas. Empty tokens are discarded, but non-empty tokens are not trimmed. Thus A,,B, selects A and B, while A, B looks for the literal field name with a leading space and normally raises. Duplicate tokens append a field more than once. An empty argument yields an empty result.

Each token is passed to required Fields.FieldByName, whose normal lookup is case-insensitive but untrimmed. Unknown names raise before a normal result is returned.

Concatenation and collisions

The method reuses the dataset's private 400-character-growth builder, resets Position to zero, and appends every selected AsString with no separator, name, length, type or null marker. Distinct selected values can collide (1+23 versus 12+3), and null commonly collides with empty text. Locale/field formatting also affects output.

The token list is freed in a finally block. That block also copies the partial builder text to the local Result, but an exception is still re-raised; callers do not receive the partial result.

Performance

Cost is proportional to the argument length, number of tokens and rendered field length. Named lookups lowercase/hash each token. Builder capacity persists after large results.

External references

Created 2026-07-15