(Swift 3,4,5...) Chilkat Zip API Concepts

This example helps clarify some common misconceptions w/ using the Chilkat Zip API.

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

    let zip = CkoZip()!

    // To clarify some concepts, this example will create a new .zip containing 2 files.

    // The NewZip method is called to initialize the zip object to a new and empty state.
    // It does not actually create the .zip file.  It simply intializes the object.
    // if the zip object did not contain anything previously, then this method could be skipped
    // altogether.  It has the side-effect of setting the zip.FileName property.
    var success: Bool = zip.newZip("test.zip")
    if success != true {
        print("\(zip.lastErrorText!)")
        return
    }

    // The FileName property should now contain "test.zip".  This is the name of the .zip
    // that is written when WriteZip or WriteZipAndClose is called.
    print("zip filename = \(zip.fileName!)")

    // When a file is "appended" to the zip object, we are really just appending a reference
    // to the file in the filesystem.  A "zip entry" is added to the zip object and this entry
    // can be one of several types.  It can point to a file.  It can contain uncompressed binary
    // or text data, it can point to an entry in the already-opened zip (if we had called OpenZip 
    // instead), etc.  

    // Now.. add a reference to a single file by calling AppendOneFileOrDir
    // Note: On Windows, forward slashes are equivalent to backslashes
    var saveExtraPath: Bool = false
    success = zip.appendOneFileOrDir("/temp/abc123/HelloWorld123.txt", saveExtraPath: saveExtraPath)
    if success != true {
        print("\(zip.lastErrorText!)")
        return
    }

    // We now have a zip object with one entry, which points to the file /temp/abc123/HelloWorld123.txt
    // If desired, we could change the filename of the zip entry so that when the zip is written,
    // the file has a different name:
    var entry: CkoZipEntry? = zip.getEntryByIndex(0)
    entry.fileName = "helloWorld.txt"
    entry = nil

    // When the zip is actually written, the entry's data will stream from /temp/abc123/HelloWorld123.txt
    // and be compressed into an entry within the .zip having the filename "helloWorld.txt"

    // Now add another entry, this time from a string containing the file content:
    entry = zip.appendString2("HelloWorld2.txt", str: "hello world!", charset: "utf-8")
    entry = nil

    // Examine the entries in the zip so far..
    // Each entry can be one of the following types:

    // 0 -- Mapped Entry: An entry in an existing Zip file.
    // 1 -- File Entry: A file not yet in memory, but referenced. 
    //      These entries are added by calling AppendFiles, AppendFilesEx, AppendOneFileOrDir, etc.
    // 2 -- Data Entry: An entry containing uncompressed data from memory. 
    //      These entries are added by calling AppendData, AppendString, etc.
    // 3 -- Null Entry: An entry that no longer exists in the .zip.
    // 4 -- New Directory Entry: A directory entry added by calling AppendNewDir. 

    var i: Int
    var n: Int = zip.numEntries.intValue
    for i = 0; i <= n - 1; i++ {

        entry = zip.getEntryByIndex(i)
        print("\(entry!.fileName!), type=\(entry!.entryType.intValue)")
        entry = nil
    }

    // Write the "test.zip" file.
    success = zip.write()
    if success != true {
        print("\(zip.lastErrorText!)")
        return
    }

    // Our zip object still contains 2 entries, but now they point to the entries within the 
    // test.zip  (We called WriteZip, which writes the .zip but does not close it.  Instead,
    // the entries of the zip object are updated to become "mapped" entries.
    // For example:

    n = zip.numEntries.intValue
    for i = 0; i <= n - 1; i++ {

        entry = zip.getEntryByIndex(i)
        print("\(entry!.fileName!), type=\(entry!.entryType.intValue)")
        entry = nil
    }

    // Finally, close the zip
    zip.close()

}