navigation bar right bar button items spacing

I solved my problem in this way:

var searchImage = UIImage(named: "search-selected")!
var clipImage = UIImage(named: "clip")!
var pencilImage = UIImage(named: "pencil")!

let searchBtn: UIButton = UIButton.buttonWithType(UIButtonType.Custom) as! UIButton
searchBtn.setImage(searchImage, forState: UIControlState.Normal)
searchBtn.addTarget(self, action: "searchBtnPressed", forControlEvents: UIControlEvents.TouchUpInside)
searchBtn.frame = CGRectMake(0, 0, 30, 30)
let searchBarBtn = UIBarButtonItem(customView: searchBtn)

let clipBtn: UIButton = UIButton.buttonWithType(UIButtonType.Custom) as! UIButton
clipBtn.setImage(clipImage, forState: UIControlState.Normal)
clipBtn.addTarget(self, action: "clipBtnPressed", forControlEvents: UIControlEvents.TouchUpInside)
clipBtn.frame = CGRectMake(0, 0, 30, 30)
let clipBarBtn = UIBarButtonItem(customView: clipBtn)

let pencilBtn: UIButton = UIButton.buttonWithType(UIButtonType.Custom) as! UIButton
pencilBtn.setImage(pencilImage, forState: UIControlState.Normal)
pencilBtn.addTarget(self, action: "pencilBtnPressed", forControlEvents: UIControlEvents.TouchUpInside)
pencilBtn.frame = CGRectMake(0, 0, 30, 30)
let pencilBarBtn = UIBarButtonItem(customView: pencilBtn)

self.navigationItem.setRightBarButtonItems([pencilBarBtn, clipBarBtn, searchBarBtn], animated: false)

Now it looks good,

Update for Swift 4.1

let testButton : UIButton = UIButton.init(type: .custom)
testButton.setImage(editImage, for: .normal)
testButton.addTarget(self, action: #selector(didTapCameraButton), for: .touchUpInside)
testButton.frame = CGRect(x: 0, y: 0, width: 30, height: 30)
let addButton = UIBarButtonItem(customView: testButton)

For Swift 3:

let searchBtn: UIButton = UIButton(type: UIButtonType.custom)
searchBtn.setImage(UIImage(named: "search"), for: [])
searchBtn.addTarget(self, action: #selector(ViewController.searchBtnPressed(_:)), for: UIControlEvents.touchUpInside)
searchBtn.frame = CGRect(x: 0, y: 0, width: 30, height: 30)
let searchButton = UIBarButtonItem(customView: searchBtn)

let clipBtn: UIButton = UIButton(type: UIButtonType.custom)
clipBtn.setImage(UIImage(named: "clip"), for: [])
clipBtn.addTarget(self, action: #selector(ViewController.clipBtnPressed(_:)), for: UIControlEvents.touchUpInside)
clipBtn.frame = CGRect(x: 0, y: 0, width: 30, height: 30)
let clipButton = UIBarButtonItem(customView: clipBtn)

let pencilBtn: UIButton = UIButton(type: UIButtonType.custom)
pencilBtn.setImage(UIImage(named: "pencil"), for: [])
pencilBtn.addTarget(self, action: #selector(ViewController.pencilBtnPressed(_:)), for: UIControlEvents.touchUpInside)
pencilBtn.frame = CGRect(x: 0, y: 0, width: 30, height: 30)
let pencilButton = UIBarButtonItem(customView: pencilBtn)

self.navigationItem.rightBarButtonItems = [pencilButton, clipButton, searchButton]

Replace ViewController with your view controller