Dart 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. Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // 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

  final pdf = CkPdf();
  try {
    pdf.loadFile('qa_data/pdf/invoice_template.pdf');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Values for every placeholder except {{po}} (the purchase order number, which this customer has none of).
  final json = CkJsonObject();
  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');

  final jsonOut = CkJsonObject();

  // The default, "error": the unfilled {{po}} is a problem and nothing would be applied.
  try {
    pdf.textReplace('check', json, jsonOut);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('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');
  try {
    pdf.textReplace('check', json, jsonOut);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('keep: ok = ${jsonOut.boolOf('ok')}');

  // "blank": {{po}} is replaced by nothing, leaving "PO Number:" with an empty value.
  json.updateString('unusedPlaceholders', 'blank');
  try {
    pdf.textReplace('apply', json, jsonOut);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('blank: applied = ${jsonOut.boolOf('applied')}');

  try {
    pdf.writeFile('qa_output/invoice_no_po.pdf');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Sample output:

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