我已经在将碰撞处理封装到一个处理程序类中,这与在该示例代码中处理碰撞的方式非常相似.
在这个项目中,我找到了一个名为RPColliderType的结构的代码：
struct RPColliderType: OptionSetType,Hashable,CustomDebugStringConvertible {
// MARK: Static properties
/// A dictionary to specify which `ColliderType`s should be notified of contacts with other `ColliderType`s.
static var requestedContactNotifications = [RPColliderType: [RPColliderType]]()
/// A dictionary of which `ColliderType`s should collide with other `ColliderType`s.
static var definedCollisions = [RPColliderType: [RPColliderType]]()
// MARK: Properties
let rawValue: UInt32
// MARK: Options
static var Obstacle: RPColliderType { return self.init(rawValue: 1 << 0) }
static var PlayerBot: RPColliderType { return self.init(rawValue: 1 << 1) }
static var TaskBot: RPColliderType { return self.init(rawValue: 1 << 2) }
// MARK: Hashable
var hashValue: Int {
return Int(rawValue)
}
// MARK: SpriteKit Physics Convenience
/// A value that can be assigned to a 'SKPhysicsBody`'s `categoryMask` property.
var categoryMask: UInt32 {
return rawValue
}
/// A value that can be assigned to a 'SKPhysicsBody`'s `collisionMask` property.
var collisionMask: UInt32 {
// Combine all of the collision requests for this type using a bitwise or.
let mask = RPColliderType.definedCollisions[self]?.reduce(RPColliderType()) { initial,colliderType in
return initial.union(colliderType)
}
// Provide the rawValue of the resulting mask or 0 (so the object doesn't collide with anything).
return mask?.rawValue ?? 0
}
/// A value that can be assigned to a 'SKPhysicsBody`'s `contactMask` property.
var contactMask: UInt32 {
// Combine all of the contact requests for this type using a bitwise or.
let mask = RPColliderType.requestedContactNotifications[self]?.reduce(RPColliderType()) { initial,colliderType in
return initial.union(colliderType)
}
// Provide the rawValue of the resulting mask or 0 (so the object doesn't need contact callbacks).
return mask?.rawValue ?? 0
}
// MARK: ContactNotifiableType Convenience
/**
Returns `true` if the `ContactNotifiableType` associated with this `ColliderType` should be
notified of contact with the passed `ColliderType`.
*/
func notifyOnContactWithColliderType(colliderType: RPColliderType) -> Bool {
if let requestedContacts = RPColliderType.requestedContactNotifications[self] {
return requestedContacts.contains(colliderType)
}
return false
}
}
每次设置SKPhysicsBody的.collisionBitmask / .contactBitmask / .categoryBitmask属性时都会使用此结构:(我已使用组件和实体设计指南实现了这一点)
class RPPhysicsComponent: GKComponent {
var physicsBody: SKPhysicsBody
init(physicsBody: SKPhysicsBody,colliderType: RPColliderType) {
self.physicsBody = physicsBody
self.physicsBody.categoryBitMask = colliderType.categoryMask
self.physicsBody.collisionBitMask = colliderType.collisionMask
self.physicsBody.contactTestBitMask = colliderType.contactMask
}
}
到现在为止还挺好.来自Objective-C我的问题是我不完全理解RPColliderType Struct之后的代码行：
/// A value that can be assigned to a 'SKPhysicsBody`'s `collisionMask` property.
var collisionMask: UInt32 {
// Combine all of the collision requests for this type using a bitwise or.
let mask = RPColliderType.definedCollisions[self]?.reduce(RPColliderType()) { initial,colliderType in
return initial.union(colliderType)
}
// Provide the rawValue of the resulting mask or 0 (so the object doesn't collide with anything).
return mask?.rawValue ?? 0
}
这是否意味着每次我调用计算(这是他们在swift中调用的,对吧？)属性 – 当我将它分配给SKPhysicsBody时我会这样做 – 它将它添加到那些静态类词典中.但我在解释’mask’/’reduce’/’union’命令时遇到了问题.
这到底是做什么的？
解决方法
但是首先,让我们添加一个PlayerBotBot应该与DefineCollisions字典碰撞的RPColliderType对象数组：
RPColliderType.definedCollisions[.PlayerBot] = [.Obstacle,.TaskBot]
此时,definedCollisions字典包含一个单独的项目,其中PlayerBot和[.Obstacle,.TaskBot]分别作为键和值.可以把它想象成可以与PlayerBot碰撞的类别是Obstacle和TaskBot.
我们现在可以使用.PlayerBot从字典中检索值(即数组)：
let array = RPColliderType.definedCollisions[.PlayerBot]
由于collisionMask是在RPColliderType中定义的,因此self用作字典键.此外,数组是可选的,因为对应于该键的值可能不存在于字典中.
然后,代码使用reduce方法将RPColliderType对象数组合成一个RPColliderType对象. reduce有两个参数：一个初始值(与数组元素的类型相同)和一个以值作为参数并返回值的函数(或闭包).在这种情况下,初始值是一个新的RPColliderType对象,闭包的参数和返回值也是RPColliderType对象：
array?.reduce(RPColliderType(),aFunction)
Apple的代码使用尾随闭包而不是传递函数来减少.从文档中,
If you need to pass a closure expression to a function as the function’s final argument and the closure expression
is long,it can be useful to write it as a trailing closure instead. A trailing closure is a closure expression that is
written outside of (and after) the parentheses of the function call it supports.
reduce迭代数组并使用初始值和每个数组元素作为参数调用闭包,返回的值用作下一次迭代的初始值：
let mask = array?.reduce(RPColliderType()) {
initial,colliderType in
return initial.union(colliderType)
}
其中initial保持RPColliderType数组元素的中间并集,colliderType是数组的当前元素.
此时,mask是一个RPColliderType对象,我们可以将其转换为UInt32
mask?.rawValue
这是collisionMask计算属性的返回值.
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