React Native

Fetch an IMAP Attachment into a BinData

Demonstrates the Chilkat Imap.FetchAttachmentBd method, which stores one attachment's bytes in a BinData object. The first argument is the Email, the second is the zero-based attachment index, and the third is the BinData, which is cleared before the operation. This example fetches the first attachment and prints its byte count.

Background: A BinData holds raw bytes, so it works for any attachment type — image, PDF, zip, and so on. From there you can save it, hash it, or hand it to another API expecting a byte buffer, all without touching the filesystem. Use the string/StringBuilder variants only when the attachment is known to be text.

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React Native

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

async function chilkatExample() {
  // Demonstrates the Imap.FetchAttachmentBd method, which downloads one attachment's bytes into
  // a BinData object.  The 1st argument is the Email, the 2nd is the zero-based attachment
  // index, and the 3rd is the BinData (which is cleared first).
  // 
  // The message is fetched headers-only, then the attachment is downloaded on demand.

  const imap = new Imap();

  imap.ssl = true;
  imap.port = 993;

  try {
    await imap.connectAsync('imap.example.com');
  } catch {
    console.log(imap.lastErrorText);
    return;
  }

  try {
    await imap.loginAsync('user@example.com', 'myPassword');
  } catch {
    console.log(imap.lastErrorText);
    return;
  }

  try {
    await imap.selectMailboxAsync('Inbox');
  } catch {
    console.log(imap.lastErrorText);
    return;
  }

  // Fetch only the message headers.  Attachment bodies are NOT downloaded, but the ckx-imap-*
  // metadata describing the attachments is present, so the attachment info methods still work.
  const headersOnly = true;
  const useUid = false;
  const seqNum = 1;
  const email = new Email();
  try {
    await imap.fetchEmailAsync(headersOnly, seqNum, useUid, email);
  } catch {
    console.log(imap.lastErrorText);
    return;
  }

  const numAttach = imap.getMailNumAttach(email);
  if (numAttach > 0) {
    // Download just the first attachment's bytes from the server into a BinData.
    const bd = new BinData();
    try {
      await imap.fetchAttachmentBdAsync(email, 0, bd);
    } catch {
      console.log(imap.lastErrorText);
      return;
    }

    console.log(`Attachment size: ${bd.numBytes} bytes`);
  }

  try {
    await imap.disconnectAsync();
  } catch {
    console.log(imap.lastErrorText);
    return;
  }
}