How do you pass data between operations in swift

I am trying to learn swift. I am currently looking at operations. I can queue up a series of operations and they run. Where I run into a problem is trying to pass data between operations. My getVOOCSVData operation retrieves the correct data which I can confirm by placing a print statement in its completion block. Unfortunately, I cannot figure out how to pass this retrieved data onto the next operation. The next operation (convertStringToArray) runs but the data I attempt to pass in is empty. Below are my operation setup and ConvertStringToArray2 class which is assigned to the convertStringToArray variable.

// operation setup
struct VOOModel {
    init() {
        let operationQueue = OperationQueue()
        let checkForUpdatedVOOData = IsUpdatedVOODataAvailable()
        checkForUpdatedVOOData.completionBlock = {
            print("Updated CSV Data = \(checkForUpdatedVOOData.updatedCSVData)")
            print("Latest Date = \(checkForUpdatedVOOData.latestCSVDate)")
        }
        let getVOOCSVData = GetVOOCSVData()
        getVOOCSVData.addDependency(checkForUpdatedVOOData)
        getVOOCSVData.completionBlock = {
            print("completion block get voo csv data")
            print("\(getVOOCSVData.csvData)") // prints out all of the data correctly
        }
        let convertStringToArray = ConvertStringToArray2(csvData: getVOOCSVData.csvData)
        convertStringToArray.addDependency(getVOOCSVData)
        convertStringToArray.completionBlock = {
            print("completion block convert string to array")
        }
        operationQueue.addOperations([checkForUpdatedVOOData, getVOOCSVData, convertStringToArray], waitUntilFinished: true)
    } // end init
} // end structure

// operation class
final class ConvertStringToArray2: Operation {
    var localData: String
    var sortedDataArray : [IndexFund] = []
    init(csvData: String) {
        localData = csvData
    }
    override func main() {
        var dataArray = [IndexFund]()
        var rows = localData.components(separatedBy: "\n")  // gives rows a value of 1
        rows.removeFirst()
        for row in rows {
            let columns = row.components(separatedBy: ",")
            if columns.count == 6 {
                let theDate = columns[0].replacingOccurrences(of: "-", with: "")
                let timeStamp = stringDateFormatter.date(from: theDate)!
                let open = Double(columns[1])!
                let high = Double(columns[2])!
                let low = Double(columns[3])!
                let close = Double(columns[4])!
                let theVolume = columns[5].trimmingCharacters(in: CharacterSet.whitespacesAndNewlines)
                let volume = Int64(theVolume)
                let fundValuesByDay = IndexFund(
                    timeStamp: timeStamp,
                    open: open,
                    high: high,
                    low: low,
                    close: close,
                    volume: volume!)
                dataArray.append(fundValuesByDay)
            }
            sortedDataArray = dataArray.sorted {
                $0.timeStamp < $1.timeStamp
            }
        }
    }
}