React Native

Get the Nth Binary Part of a Content-Type into BinData

Demonstrates the Chilkat Email.GetNthBinaryPartOfTypeBd method, which loads the binary bytes of the Nth MIME sub-part matching a content-type pattern into a BinData object. The arguments are the zero-based index among the matching parts, the content-type pattern, an inlineOnly flag, an excludeAttachments flag, and the BinData that receives the bytes. This example extracts the first image/png part.

Background: This is the binary, type-targeted way to pull a specific part out of a message — ideal for extracting, say, every image/png or the one application/pdf from a complex MIME tree without caring whether it is an attachment, an inline image, or a body part. Reading into a BinData keeps the raw bytes exact, ready to save, hash, or re-transmit.

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import { BinData, Email } from '@chilkat/react-native'

function chilkatExample() {
  // Demonstrates the GetNthBinaryPartOfTypeBd method, which loads the binary bytes of the Nth
  // MIME sub-part matching a Content-Type pattern into a BinData object.  The arguments are
  // the zero-based index among matching parts, the Content-Type pattern, inlineOnly,
  // excludeAttachments, and the BinData that receives the bytes.

  const email = new Email();
  email.subject = 'GetNthBinaryPartOfTypeBd example';
  email.body = 'See the attached image.';

  // Load the image from a file into a BinData object and attach it (binary data belongs
  // in a BinData, never in a string).
  const bdImage = new BinData();
  try {
    bdImage.loadFile('qa_data/images/photo.png');
  } catch {
    console.log(bdImage.lastErrorText);
    return;
  }

  try {
    email.addAttachmentBd('photo.png', bdImage, 'image/png');
  } catch {
    console.log(email.lastErrorText);
    return;
  }

  // Load the bytes of the first (index 0) image/png part into a BinData object.
  const bd = new BinData();
  try {
    email.getNthBinaryPartOfTypeBd(0, 'image/png', false, false, bd);
  } catch {
    console.log(email.lastErrorText);
    return;
  }

  console.log(`image/png part size (bytes) = ${bd.numBytes}`);

  // Note: The path "qa_data/images/photo.png" is a relative local filesystem path,
  // relative to the current working directory of the running application.
}