(Swift 3,4,5...) How to Download Messages in MessageSet One at a Time

If a message set contains a huge number of emails, it's NOT a good idea to try to download all at once into an email bundle using a method such as FetchBundle. It's better to iterate over the messages in the set to download one by one.

Chilkat Downloads for the Swift Programming Language MAC OS X (Cocoa) Objective-C/Swift Libs iOS Objective-C/Swift Libs

func chilkatTest() {
    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    let imap = CkoImap()!

    // Connect using TLS.
    imap.ssl = true
    imap.port = 993
    var success: Bool = imap.connect("imap.example.com")
    if success != true {
        print("\(imap.lastErrorText!)")
        return
    }

    // Authenticate
    success = imap.login("email_account_login", password: "email_account_password")
    if success != true {
        print("\(imap.lastErrorText!)")
        return
    }

    // Select an IMAP mailbox
    success = imap.selectMailbox("Inbox")
    if success != true {
        print("\(imap.lastErrorText!)")
        return
    }

    // Search for messages and return a set of matching messages.
    // (This example will simply search for ALL messages.)
    var fetchUids: Bool = true
    var messageSet: CkoMessageSet? = imap.search("ALL", bUid: fetchUids)
    if imap.lastMethodSuccess != true {
        print("\(imap.lastErrorText!)")
        return
    }

    print("Number of messages = \(messageSet!.count.intValue)")

    var i: Int = 0
    while i < messageSet!.count.intValue {
        var email: CkoEmail? = imap.fetchSingle(messageSet!.getId(i), bUid: fetchUids)
        if imap.lastMethodSuccess != true {
            print("\(imap.lastErrorText!)")
            messageSet = nil
            return
        }

        print("\(email!.from!); \(email!.subject!)")
        email = nil

        i = i + 1
    }

    messageSet = nil

    print("OK")

}