parâmetrosListaOptional
Names between the vertical bars. They are local to the block and receive the supplied arguments.
FOUNDATIONPublished
Code blocks (CodeBlock)
{ |[parâmetros]| [expressão1, expressão2, ...] }Create storable anonymous functions, receive parameters and evaluate expressions on demand with Eval().
Overview
A code block is an AdvPL value of type B (Block), similar to an anonymous function. It may receive parameters and execute one or more comma-separated expressions. Eval() executes the block and returns the result of its last expression. Unlike a regular function, its body accepts expressions and function calls, but not language commands.
Syntax
{ |[parâmetros]| [expressão1, expressão2, ...] }Parameters
expressõesAdvPLOptional
One or more comma-separated AdvPL expressions, executed from left to right.
retornoQualquerOptional
The result of the last expression; an empty block returns NIL.
Simple block with a return value
User Function ExBlockSum()
Local bAdd := { |nValue1, nValue2| Abs(nValue1) + Abs(nValue2) }
Local nResult := Eval(bAdd, 10, -20)
ConOut("Result: " + CValToChar(nResult))
ReturnExpected result
Eval() supplies two arguments and receives 30, the result of the last expression.
Multiple expressions
User Function ExBlockList()
Local bCalculate := { |nValue| ConOut("Received: " + CValToChar(nValue)), nValue * 2 }
Local nResult := Eval(bCalculate, 5)
MsgInfo("Double: " + CValToChar(nResult))
ReturnExpected result
Expressions run from left to right and the return value is 10, the result of the last expression.
Custom sorting with ASort
User Function ExOrdenacao()
Local aNomes := {"CARLA", "ANDREA", "BEATRIZ"}
Local bDecrescente := { |cNome1, cNome2| cNome1 > cNome2 }
ASort(aNomes, , , bDecrescente)
ReturnExpected result
The block compares pairs selected by ASort() and enables descending order.
Pass by reference
User Function ExReferencia()
Local bIncrementar := { |nValor| nValor += 1 }
Local nContador := 0
Eval(bIncrementar, nContador) // nContador continua 0
Eval(bIncrementar, @nContador) // nContador passa a 1
ReturnExpected result
Without @, the block receives a copy; with @, its change reaches the original variable.
Capturing a local variable
User Function ExContexto()
Local nContador := 0
Local bSomar := { |nValor| nContador += nValor }
Eval(bSomar, 5)
ConOut("Contador: " + CValToChar(nContador))
ReturnExpected result
The block references and changes nCounter in the Local context where it was created.
- Braces delimit the block and two vertical bars delimit its parameter list, even when empty.
- Block parameters have scope restricted to the block itself.
- Eval(bBlock, arguments...) executes the content; @ passes a variable by reference.
- Blocks are used for visual component events, sorting, evaluations and other APIs that receive behavior as an argument.
- A block may capture a Local variable visible when it is created and retain that context while referenced.
- { .T. } and { IIF(...) } are one-element arrays, not code blocks; they lack vertical bars.
- Avoid large blocks: extract the logic into a function and let the block call it.
- The official reference advises against calling a Static Function inside a block that may run from another source file because duplicate static names may cause indeterminate behavior.
- Keeping a block that captured Local context for a long time may retain its memory area; remove references with NIL when no longer needed.
- Follow the parameter count and return type expected by the function that evaluates the block.