1.动态计算字符串所占区域

  func heightForComment(font: UIFont, width: CGFloat) -> CGFloat {
    let rect = NSString(string: comment).boundingRectWithSize(CGSize(width: width, height: CGFloat(MAXFLOAT)), options: .UsesLineFragmentOrigin, attributes: [NSFontAttributeName: font], context: nil)
    return ceil(rect.height)
  }

---

2.计算一个图片放在另一个 view 按照一定的比例定宽动态取高

let photo = photos[indexPath.item]
let boundingRect =  CGRect(x: 0, y: 0, width: width, height: CGFloat(MAXFLOAT))
let rect  = AVMakeRectWithAspectRatioInsideRect(photo.image.size, boundingRect)

---

3.利用map函数NSArray转Array<String>

        let filePath = NSBundle.mainBundle().pathForResource("citydict", ofType: "plist")
        let cityDict = NSDictionary(contentsOfFile: filePath!)
        
        let keys = cityDict.allKeys.map({ object -> String in
            return object as! String
        }).sort()

---

4.UIImageJPEGRepresentation压缩图片

extension UIImage { 
  var uncompressedPNGData: NSData { return UIImagePNGRepresentation(self)! } 
  var highestQualityJPEGNSData: NSData { return UIImageJPEGRepresentation(self, 1.0)! } 
  var highQualityJPEGNSData: NSData { return UIImageJPEGRepresentation(self, 0.75)! } 
  var mediumQualityJPEGNSData: NSData { return UIImageJPEGRepresentation(self, 0.5)! } 
  var lowQualityJPEGNSData: NSData { return UIImageJPEGRepresentation(self, 0.25)! } 
  var lowestQualityJPEGNSData:NSData { return UIImageJPEGRepresentation(self, 0.0)! }
}

---

5.修改图片大小

extension UIImage{
    
    func resizeImage(newSize:CGSize)->UIImage{
        
        guard self.size != size else { return self }
       
        UIGraphicsBeginImageContextWithOptions(newSize, false, 0.0);
        self.drawInRect(CGRectMake(0, 0, newSize.width, newSize.height))
        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return newImage
    }
}

---

6.UIBezierPath绘制圆形

center：弧线圆心坐标
radius：弧线半径
**startAngle：
**弧线起始角度
**endAngle：
**弧线结束角度
clockwise：是否顺时针绘制

path.addArcWithCenter(CGPoint(x: size.width / 2, y: size.height / 2),
                                  radius:size.width / 2,
                                  startAngle:CGFloat(-3 * M_PI_4),
                                  endAngle:CGFloat(-M_PI_4),
                                  clockwise:true)

---

7.代码单独设置view宽高约束 方便利用来动态改变view的宽高

 let heightContraints = NSLayoutConstraint(item: customView, attribute: .Height, relatedBy: .Equal, toItem: nil, attribute: NSLayoutAttribute.NotAnAttribute, multiplier: 1.0, constant: 70) let widthContraints = NSLayoutConstraint(item: customView, attribute: .Width, relatedBy: .Equal, toItem: nil, attribute: NSLayoutAttribute.NotAnAttribute, multiplier: 1.0, constant: 70)