CharacterCOptional
Text delimited by single or double quotes.
FOUNDATIONPublished
AdvPL variable types
Local <variável> := <valor> · ValType(<variável>)Learn how to create, name, initialize, and assign AdvPL variables and how their type follows the stored value.
Overview
A variable is a named reference to a value held in memory during execution. In traditional AdvPL, its type is dynamic: it is determined by the assigned value and may change during the variable lifetime. This differs from scope, which controls visibility and lifetime, and explicit As <type> typing, which documents and constrains the expected contract.
Syntax
Local <variável> := <valor> · ValType(<variável>)Parameters
NumericNOptional
Integer or decimal floating-point number.
DateDOptional
A date created by Date(), CToD(), SToD(), or another date function.
LogicalLOptional
True (.T.) or false (.F.).
ArrayAOptional
A one-based indexed collection that may contain mixed types.
CodeBlockBOptional
A set of expressions that can later be run with Eval().
ObjectOOptional
An instance of a class.
NILUOptional
Absence of a value; the usual initial state of an uninitialized declared variable.
Declaration and initialization
User Function ExVariables()
Local cProduct := "Keyboard"
Local nQuantity := 2
Local nPrice := 150.50
Local lAvailable := .T.
Local dCreated := Date()
If lAvailable
MsgInfo(cProduct + " - total: " + ;
CValToChar(nQuantity * nPrice))
EndIf
ReturnExpected result
Each variable receives an initial value that matches the intent communicated by its prefix.
NIL before initialization
User Function ExNil()
Local nPercentage
Local nResult
If ValType(nPercentage) == "U"
nPercentage := 10
EndIf
nResult := 250 * (1 + nPercentage / 100)
MsgInfo("Result: " + CValToChar(nResult))
ReturnExpected result
ValType() returns U while the variable has no value; initialization prevents NIL from entering the calculation.
Dynamic type change
User Function ExTipoDinamico()
Local xValor := "Pedido aberto"
ConOut("Tipo atual: " + ValType(xValor)) // C
xValor := 22
ConOut("Tipo atual: " + ValType(xValor)) // N
xValor := .T.
ConOut("Tipo atual: " + ValType(xValor)) // L
xValor := Date()
ConOut("Tipo atual: " + ValType(xValor)) // D
ReturnExpected result
The same variable holds different types. This flexibility should be intentional.
Conversion before concatenation
User Function ExConversao()
Local nQuantidade := 3
Local dHoje := Date()
Local lAtivo := .T.
ConOut("Quantidade: " + CValToChar(nQuantidade))
ConOut("Data: " + DToC(dHoje))
ConOut("Ativo: " + IIf(lAtivo, "sim", "não"))
ReturnExpected result
Each value is converted to character before it is joined to text.
Implicit assignment to avoid
User Function ExErroDigitacao()
Local nQuantidade := 10
nQuantidad := 20 // nome incorreto: pode criar uma Private
MsgInfo("Quantidade: " + CValToChar(nQuantidade))
ReturnExpected result
A missing letter may create another identifier rather than update nQuantity.
- Declare and initialize in the same statement when a clear initial value exists.
- Prefer := for assignment so it is visually distinct from = and == comparisons.
- ValType(xValue) returns a letter for the current type and may change after another assignment.
- Use consistent c, n, d, l, a, b, o, and x prefixes to communicate intent.
- Consulted documentation records a ten-character identifier rule. Treat it as historical compatibility behavior and verify it on the AppServer version in use.
- Keep concepts separate: type describes the value; scope controls visibility; lifetime determines how long the variable exists.
- An uninitialized declaration produces NIL, which may cause type mismatch in calculations or concatenation.
- Assigning to an undeclared name may implicitly create a Private variable, so a typo can silently change program logic.
- Changing types freely reduces predictability. Do it only intentionally and validate with ValType().
- Convert numbers, dates, logical values, and NIL before concatenating them with text.
- Do not use reserved words, spaces, or special characters in identifiers.
- Store is retained for historical compatibility; prefer explicit declarations and := in new code.