FUNCTIONUnder review

EXISTCHAV()

ExistChav( alias, expressao, [indice], [help] ) --> lRet

Validates key uniqueness.

EXISTCHAV()AdvPL

01 · OVERVIEW

Overview

ExistChav approves an absent key and rejects a duplicate. Supply the expression without branch as documented; do not automatically reuse a DBSeek key. Omitted index uses the first index. Rejection can display help, so this is not a generic silent lookup. The GitHub source demonstrates SA1 code/store calls; this proposal uses a parameterized callback without querying real records. Prevalidation alone does not solve concurrency or transactional uniqueness. (TOTVS, n.d., ref. 1)

02 · SYNTAX

Syntax

ExistChav( alias, expressao, [indice], [help] ) --> lRet

Parameters

alias

CharacterRequired

Validation alias.

expressao

CharacterRequired

Key without branch.

indice

NumericOptional

Order matching the expression.

help

CharacterOptional

Rejection help name.

Return value

True when its rule is satisfied; false on rejection.

03 · PRACTICAL EXAMPLE

Commented example

#Include "Protheus.ch"

User Function Ed373()
    Local bValidate := {|cAlias,cKey,nOrder| ExistChav(cAlias,cKey,nOrder)}
    // Branch-free key and matching order; do not evaluate here.
Return Nil

Expected result

Block prepared without lookup; return meaning depends on each function’s rule. Under review: editorial example neither compiled nor run in Protheus. Check includes, release, RDD and context before testing.

BEST PRACTICES

Confirm release-specific validation context, order and messages. Do not confuse the two logical meanings.
Under review: editorial example neither compiled nor run in Protheus. Check includes, release, RDD and context before testing.