UIDynamicBehavior

import Foundation
import UIKit

//
//  UIDynamicBehavior.h
//  UIKit
//
//  Copyright (c) 2012-2015 Apple Inc. All rights reserved.
//

@available(iOS 9.0, *)
public enum UIDynamicItemCollisionBoundsType : UInt {
    
    case Rectangle
    case Ellipse // radii will be determined from the items bounds width, height
    case Path
}

public protocol UIDynamicItem : NSObjectProtocol {
    
    public var center: CGPoint { get set }
    public var bounds: CGRect { get }
    public var transform: CGAffineTransform { get set }
    
    /**
     The collision type represents how the dynamics system will evaluate collisions with 
     respect to the dynamic item. defaults to UIDynamicItemCollisionBoundsTypeRectangle
     */
    @available(iOS 9.0, *)
    optional public var collisionBoundsType: UIDynamicItemCollisionBoundsType { get }
    
    /**
     The path must represent a convex polygon with counter clockwise winding and no self intersection. 
     The point (0,0) in the path corresponds to the dynamic item's center.
     */
    @available(iOS 9.0, *)
    optional public var collisionBoundingPath: UIBezierPath { get }
}

@available(iOS 9.0, *)
public class UIDynamicItemGroup : NSObject, UIDynamicItem {
    
    public init(items: [UIDynamicItem])
    
    public var items: [UIDynamicItem] { get }
}

@available(iOS 7.0, *)
public class UIDynamicBehavior : NSObject {
    
    // 添加子行为（主要是让他自定义 behavior ）
    public func addChildBehavior(behavior: UIDynamicBehavior)
    // 移除子行为
    public func removeChildBehavior(behavior: UIDynamicBehavior)
    
    // 获取所有的子行为
    public var childBehaviors: [UIDynamicBehavior] { get }
    
    // When running, the dynamic animator calls the action block on every animation step.
    // 当运行,动态动画器调用动作块在每个动画的步骤。
    // 行为
    public var action: (() -> Void)?
    
    public func willMoveToAnimator(dynamicAnimator: UIDynamicAnimator?) // nil when being removed from an animator
    
    // 获取动画执行者
    public var dynamicAnimator: UIDynamicAnimator? { get }
}