B4X Requires Chilkat v11.7.0+

PDF Placeholders Without a Value: Error, Blank or Keep

See more PDF Text Replacement Examples

Demonstrates the "unusedPlaceholders" option, which decides what happens to a placeholder found on the page that has no value in "placeholders": "error" (the default) makes it a problem with the reason unusedPlaceholder, so nothing is applied; "blank" replaces it with nothing; "keep" leaves it on the page as it is. B4X

Dim success As Boolean = False

'  This example requires the Chilkat API to have been previously unlocked.
'  See Global Unlock Sample for sample code.

'  The PDF used in this example is available at invoice_template.pdf

Dim pdf As ChilkatPdf
pdf.Initialize("pdf")
success = pdf.LoadFile("qa_data/pdf/invoice_template.pdf")
If success = False Then
    Log(pdf.LastErrorText)
    Return
End If


'  Values for every placeholder except {{po}} (the purchase order number, which this customer has none of).
Dim json As ChilkatJsonObject
json.Initialize
json.UpdateString("placeholders.customer", "Acme Corp")
json.UpdateString("placeholders.date", "2026-10-18")
json.UpdateString("placeholders.qty1", "2")
json.UpdateString("placeholders.desc1", "Cordless drill, 18 V")
json.UpdateString("placeholders.price1", "$460.00")
json.UpdateString("placeholders.amount1", "$920.00")
json.UpdateString("placeholders.qty2", "6")
json.UpdateString("placeholders.desc2", "Galvanized hinge, 4 inch")
json.UpdateString("placeholders.price2", "$12.50")
json.UpdateString("placeholders.amount2", "$75.00")
json.UpdateString("placeholders.subtotal", "$995.00")
json.UpdateString("placeholders.taxRate", "7.35%")
json.UpdateString("placeholders.tax", "$73.13")
json.UpdateString("placeholders.total", "$1,068.13")

Dim jsonOut As ChilkatJsonObject
jsonOut.Initialize

'  The default, "error": the unfilled {{po}} is a problem and nothing would be applied.
success = pdf.TextReplace("check", json, jsonOut)
If success = False Then
    Log(pdf.LastErrorText)
    Return
End If

Log("error (default): ok = " & jsonOut.BoolOf("ok") & ", problem: " & jsonOut.StringOf("problems[0].field") & " " & jsonOut.StringOf("problems[0].reason"))

'  "keep": {{po}} stays on the page, literally.
json.UpdateString("unusedPlaceholders", "keep")
success = pdf.TextReplace("check", json, jsonOut)
If success = False Then
    Log(pdf.LastErrorText)
    Return
End If

Log("keep: ok = " & jsonOut.BoolOf("ok"))

'  "blank": {{po}} is replaced by nothing, leaving "PO Number:" with an empty value.
json.UpdateString("unusedPlaceholders", "blank")
success = pdf.TextReplace("apply", json, jsonOut)
If success = False Then
    Log(pdf.LastErrorText)
    Return
End If

Log("blank: applied = " & jsonOut.BoolOf("applied"))

success = pdf.WriteFile("qa_output/invoice_no_po.pdf")
If success = False Then
    Log(pdf.LastErrorText)
    Return
End If


'  Sample output:

'  error (default): ok = false, problem: po unusedPlaceholder
'  keep: ok = true
'  blank: applied = true