swift中的extension（即為擴充套件）：是向已有的一個類、結構體或者列舉新增新功能（例項方法或者型別方法），包括在沒有獲取原始碼的情況下擴充套件型別的能力。

• 對UIView擴充套件實現swift中的xib或者storyboard視覺化（設定圓角cornerRadius、設定borderWidth等），這樣在xib或者storyboard中便可直視控制元件的相應的屬性設定效果，不要要Run之後再去看效果：

extension UIView {
    @IBInspectable var borderWidth: CGFloat {
        get {
            return self.layer
 
.borderWidth
        }
        set {
            self.layer.borderWidth = newValue
        }
    }

    @IBInspectable var borderColor: UIColor {
        get {
            return UIColor(cgColor:self.layer.borderColor!)
        }
        set {
            self.layer.borderColor = newValue.cgColor
        }
    }

    var cornerRadius: CGFloat {
        get {
            return self.layer
 
.cornerRadius
        }
        set {
            self.layer.cornerRadius = newValue
            self.layer.masksToBounds = true
        }
    }
}

• 對UIImage的擴充套件（直接可以用點語法呼叫擴充套件的屬性和方法即可）

extension UIImage {
    var height : CGFloat{return self.size.height}
    var width  : CGFloat{return self.size
 
.width}

    // 壓縮圖片
    func imageCompress(targetWidth:CGFloat) -> UIImage {
        let targetHeight = (targetWidth/width)*height
        UIGraphicsBeginImageContext(CGSize(width: targetWidth, height: targetHeight))
        self.draw(in: CGRect(x: 0, y: 0, width: targetWidth, height: targetHeight))
        let newImage : UIImage = UIGraphicsGetImageFromCurrentImageContext()!
        UIGraphicsEndImageContext()
        return newImage
    }

    //模糊圖片
    func blurImage(blurValue:NSNumber) -> UIImage {
        let context = CIContext(options: [kCIContextUseSoftwareRenderer: true])
        let ciImage = CoreImage.CIImage(image: self)
        let blurFilter = CIFilter(name: "CJGaussianBlur")
        blurFilter?.setValue(ciImage, forKey: kCIInputImageKey)
        blurFilter?.setValue(blurValue, forKey: "inputRadius")
        let imageRef = context.createCGImage((blurFilter?.outputImage)!, from: (ciImage?.extent)!)
        let newImage = UIImage(cgImage: imageRef!)
        return newImage
    }
}