titleEdgeInsets应该是最好的方法，如果只是简单的左对齐，也可以如下方法。

btn.contentHorizontalAlignment = UIControlContentHorizontalAlignmentLeft;

同样，右对齐 居中都有。

import UIKit

class ViewController: UIViewController {

override func viewDidLoad() {
    super.viewDidLoad()
    
    //创建有状态的按钮
    var btn:UIButton = UIButton(frame: CGRect(x: 50, y: 50, width: 100, height: 25))
    
    btn.setTitle("点击按钮", forState: UIControlState.Highlighted)
    btn.setTitle("未点击", forState: UIControlState.Normal)
    btn.backgroundColor = UIColor.blackColor()
    self.view.addSubview(btn)
    //给按钮添加点击事件
    btn.addTarget(self, action: "clickEvent:", forControlEvents: UIControlEvents.TouchUpInside)
    
    //创建没有状态的按钮
    var btn2:UIButton = UIButton(frame: CGRect(x: 50, y: 85, width: 100, height: 35))
    btn2.setTitle("Normal", forState: UIControlState.Normal)
    btn2.backgroundColor = UIColor.blueColor()
    self.view.addSubview(btn2)
    
    //创建一个图片加文字的按钮
    var btn3:UIButton = UIButton(frame: CGRect(x: 50, y: 130, width: 180, height: 35))
    btn3.setImage(UIImage(named: "btn1"), forState: UIControlState.Normal)
    btn3.titleLabel?.font = UIFont.boldSystemFontOfSize(30)
    btn3.imageView?.contentMode = UIViewContentMode.ScaleAspectFit
    //btn3.imageEdgeInsets = UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0)
    btn3.setTitle("图片按钮", forState: UIControlState.Normal)
    self.view.addSubview(btn3)
    
    //从系统定义的按钮类型创建Button
    var btn4:UIButton = UIButton.buttonWithType(UIButtonType.ContactAdd) as! UIButton
    //btn4.backgroundColor = UIColor.brownColor()
    btn4.frame.offset(dx: 60, dy: 200)
    self.view.addSubview(btn4)
    
    //创建禁止按钮
    var btn5:UIButton = UIButton(frame: CGRect(x: 50, y: 240, width: 100, height: 35))
    btn5.setTitle("点击按钮", forState: UIControlState.Highlighted)
    btn5.setTitle("禁止按钮", forState: UIControlState.Normal)
    btn5.enabled = false //设置按钮不能点击
    btn5.setTitleColor(UIColor.redColor(), forState: UIControlState.Disabled)//代表已经禁止
    btn5.backgroundColor = UIColor.purpleColor()
    self.view.addSubview(btn5)
    
    //创建一个圆角按钮
    var btn6:UIButton = UIButton(frame: CGRect(x: 50, y: 280, width: 100, height: 35))
    btn6.backgroundColor = UIColor.whiteColor()
    btn6.setTitleColor(UIColor.blackColor(), forState: UIControlState.Normal)
    btn6.setTitle("圆角按钮", forState: UIControlState.Normal)
    btn6.layer.cornerRadius = 5
    self.view.addSubview(btn6)
    
    //部分圆角按钮,主要是利用layer的mask属性,在通过CAShaperLayer和UIBezierPath来画
    var btn7:UIButton = UIButton(frame: CGRect(x: 50, y: 330, width: 100, height: 35))
    btn7.backgroundColor = UIColor.whiteColor()
    btn7.setTitleColor(UIColor.blackColor(), forState: UIControlState.Normal)
    btn7.setTitle("部分圆角按钮", forState: UIControlState.Normal)
    
    let shape:CAShapeLayer = CAShapeLayer()
    let bepath:UIBezierPath = UIBezierPath(roundedRect: btn6.bounds, byRoundingCorners: UIRectCorner.TopRight|UIRectCorner.TopLeft, cornerRadii: CGSize(width: 15, height: 15))
    
    UIColor.blackColor().setStroke()
    shape.path = bepath.CGPath
    
    btn7.layer.mask = shape
    self.view.addSubview(btn7)
    
    //创建折角按钮
    var btn8:UIButton = UIButton(frame: CGRect(x: 50, y: 380, width: 100, height: 35))
    btn8.backgroundColor = UIColor.whiteColor()
    
    btn8.setTitleColor(UIColor.blackColor(), forState: UIControlState.Normal)
    btn8.setTitle("折角按钮", forState: UIControlState.Normal)
    
    let shape8:CAShapeLayer = CAShapeLayer()
    let bepath8:UIBezierPath = UIBezierPath()
    bepath8.moveToPoint(CGPoint(x: 0,y: 0))
    bepath8.addLineToPoint(CGPoint(x: 80,y: 0))
    
    bepath8.addLineToPoint(CGPoint(x: 100,y: 15))
    bepath8.addLineToPoint(CGPoint(x: 100,y: 35))
    bepath8.addLineToPoint(CGPoint(x: 0,y: 35))
    bepath8.closePath()
    
    shape8.path = bepath8.CGPath
    
    btn8.layer.mask = shape8
    self.view.addSubview(btn8)
    
    //创建border按钮
    var btn9:UIButton = UIButton(frame: CGRect(x: 50, y: 420, width: 100, height: 35))
    btn9.backgroundColor = UIColor.whiteColor()
    btn9.setTitle("边框按钮", forState: UIControlState.Normal)
    btn9.setTitleColor(UIColor.blackColor(), forState: UIControlState.Normal)
    btn9.layer.borderColor = UIColor.blackColor().CGColor
    btn9.layer.borderWidth = 1
    btn9.layer.cornerRadius = 5
    self.view.addSubview(btn9)
    
    //
    
}


override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

func clickEvent(sender:AnyObject){
    NSLog("按钮点击了事件")
}

}

Snip20160722_10.png