How to use NSLog and print only for debugging? http://swiftiostutorials.com/use-nslog-debugging/

DebugPrint.swift

/// Writes the textual representations of `items` most suitable for
/// debugging, separated by `separator` and terminated by
/// `terminator`, into the standard output.
///
/// The textual representations are obtained for each `item` via
/// the expression `String(reflecting: item)`.
///
/// - Note: To print without a trailing newline, pass `terminator: ""`
///
/// - SeeAlso: `print`, `Streamable`, `CustomStringConvertible`,
///   `CustomDebugStringConvertible`
public func debugPrint(items: Any..., separator: String = default, terminator: String = default)

SwiftDebugLog.swift

// Swift 3

import Foundation

func releasePrint(_ object: Any) {
    Swift.print(object)
}

func print(_ object: Any) {
    #if DEBUG
        Swift.print(object)
    #endif
}