(Swift 3,4,5...) Get the Index of a JSON Member

This example demonstrates how to get the index of a given member by name.

{
  "name": "donut",
  "image":
    {
    "fname": "donut.jpg",
    "w": 200,
    "h": 200
    },
  "thumbnail":
    {
    "fname": "donutThumb.jpg",
    "w": 32,
    "h": 32
    }
}

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func chilkatTest() {
    let json = CkoJsonObject()!

    // This is the above JSON with whitespace chars removed (SPACE, TAB, CR, and LF chars).
    // The presence of whitespace chars for pretty-printing makes no difference to the Load
    // method. 
    var jsonStr: String? = "{\"name\": \"donut\",\"image\":{\"fname\": \"donut.jpg\",\"w\": 200,\"h\": 200},\"thumbnail\":{\"fname\": \"donutThumb.jpg\",\"w\": 32,\"h\": 32}}"

    var success: Bool = json.load(jsonStr)
    if success != true {
        print("\(json.lastErrorText!)")
        return
    }

    // The top-level JSON object has three members: name, image, and thumbnail.
    var nameIndex: Int = json.index(of: "name").intValue
    // The index of the "name" member is 0.
    print("nameIndex = \(nameIndex)")

    var thumbIndex: Int = json.index(of: "thumbnail").intValue
    // The index of the "thumbnail" member is 2.
    print("thumbIndex = \(thumbIndex)")

    // The "fname" member is NOT a direct member of the top-level JSON object.
    // It is a member of a nested object.  If we try to get the index of this
    // member using the top-level JSON object, it is not found (and returns -1).
    var fnameIndex: Int = json.index(of: "fname").intValue
    // The fnameIndex is -1 (not found).  This is correct.
    print("fnameIndex = \(fnameIndex)")

    // Get the "image" object.
    var imageObj: CkoJsonObject? = json.object(of: "image")
    if json.lastMethodSuccess == false {
        print("image object not found.")
        return
    }

    // Now we can get the index of the "fname" object, because it is a direct
    // member of the "image" object:
    fnameIndex = imageObj!.index(of: "fname").intValue
    print("fnameIndex = \(fnameIndex)")

    imageObj = nil

}