iOS-Swift扩大按钮UIButton点击范围

// MARK：扩展按钮的点击区域
import Foundation
func associatedObject(
base: AnyObject,
key: UnsafePointer,
initialiser: () -> ValueType)
-> ValueType {
if let associated = objc_getAssociatedObject(base, key)
as? ValueType { return associated }
let associated = initialiser()
objc_setAssociatedObject(base, key, associated,
.OBJC_ASSOCIATION_RETAIN)
return associated
}
func associateObject(
base: AnyObject,
key: UnsafePointer,
value: ValueType) {
objc_setAssociatedObject(base, key, value,
.OBJC_ASSOCIATION_RETAIN)
}

private var topKey: UInt8 = 0
private var bottomKey: UInt8 = 0
private var leftKey: UInt8 = 0
private var rightKey: UInt8 = 0
extension UIButton {
var top: NSNumber {
get {
return associatedObject(base: self, key: &topKey)
{ return 0 }
}
set {
associateObject(base: self, key: &topKey, value: newValue)
}
}

var bottom: NSNumber {
    get {
        return associatedObject(base: self, key: &bottomKey)
        { return 0 }
    }
    set {
        associateObject(base: self, key: &bottomKey, value: newValue)
    }
}

var left: NSNumber {
    get {
        return associatedObject(base: self, key: &leftKey)
        { return 0 }
    }
    set {
        associateObject(base: self, key: &leftKey, value: newValue)
    }
}

var right: NSNumber {
    get {
        return associatedObject(base: self, key: &rightKey)
        { return 0 }
    }
    set {
        associateObject(base: self, key: &rightKey, value: newValue)
    }
}

func setEnlargeEdge(top: Float, bottom: Float, left: Float, right: Float) -> Void {
    self.top = NSNumber.init(value: top)
    self.bottom = NSNumber.init(value: bottom)
    self.left = NSNumber.init(value: left)
    self.right = NSNumber.init(value: right)
}

func enlargedRect() -> CGRect {
    let top = self.top
    let bottom = self.bottom
    let left = self.left
    let right = self.right
    if top.floatValue >= 0, bottom.floatValue >= 0, left.floatValue >= 0, right.floatValue >= 0 {
        return CGRect.init(x: self.bounds.origin.x - CGFloat(left.floatValue),
                           y: self.bounds.origin.y - CGFloat(top.floatValue),
                           width: self.bounds.size.width + CGFloat(left.floatValue) + CGFloat(right.floatValue),
                           height: self.bounds.size.height + CGFloat(top.floatValue) + CGFloat(bottom.floatValue))
    }
    else {
        return self.bounds
    }
}

open override func point(inside point: CGPoint, with event: UIEvent?) -> Bool {
    let rect = self.enlargedRect()
    if rect.equalTo(self.bounds) {
        return super.point(inside: point, with: event)
    }
    return rect.contains(point) ? true : false
}

}