didBeginContact传递了PKPhyicsObject

Question

我有一个扩展的帮助方法 SKPhysicsContact

extension SKPhysicsContact {

    /// - returns: `[SKPhysicsBody]` containing all the bodies that match `mask`
    func bodiesMatchingCategory(mask: UInt32) -> [SKPhysicsBody] {
        let bodies = [bodyA, bodyB]
        return bodies.filter { ($0.categoryBitMask & mask) != 0 }
    }
}

在didBeginContact()我呼吁在过了这个方法contact.

func didBeginContact(contact: SKPhysicsContact) {
    let ballMask: UInt32 = 0x1 << 2
    let ball = contact.bodiesMatchingCategory(ballMask)
...

我有时会收到此错误消息(如5中的1),这会导致应用程序崩溃:

-[PKPhysicsContact bodiesMatchingCategory:]: unrecognized selector sent to instance 0x165f2350

我查了一下PKPhysicsContact,它是私人框架(链接)的一部分. SKPhysicsContact看起来它只是一个空的类定义,它只暴露了某些属性PKPhysicsContact.

我觉得这是SpriteKit团队的一个Objective-C黑客攻击,打破了Swift强大的打字.

救命？

如何确保我总是SKPhysicsContact回来？

---

我添加了一张支票来测试 SKPhysicsContact

let test = contact as Any
print("Test is: \(test)")
guard test is SKPhysicsContact else {
    return
}

哪个正确捕获类型不匹配.

事实上,它永远不会返回SKPhysicsContact!!？

---

我已尝试在Objective-C中执行此操作(由响应者建议)并且我得到相同的结果.

我对Apple Dev论坛进行了讨论,可能为未来的求职者提供一些帮助.

这是Objective-C代码供参考:

@interface SKPhysicsContact (MatchingBodies)

- (NSArray *)bodiesMatchingCategory:(UInt32)category;

@end

@implementation SKPhysicsContact (MatchingBodies)

- (NSArray *)bodiesMatchingCategory:(UInt32)category {
    NSArray *bodies = @[self.bodyA, self.bodyB];

    NSPredicate *predicate = [NSPredicate predicateWithBlock:^BOOL(SKPhysicsBody *body, NSDictionary *bindings) {
        return (body.categoryBitMask & category) != 0;
    }];
    NSArray *matching = [bodies filteredArrayUsingPredicate:predicate];
    return matching;
}

@end

叫这里:

-(void)didBeginContact:(SKPhysicsContact *)contact
{
    static const uint32_t MarbleContact = 0x1 <<1;  // 2
    static const uint32_t GoalContact = 0x1 <<2;    // 4

    SKPhysicsBody *ball = [contact bodiesMatchingCategory:MarbleContact].firstObject;
    NSLog(@"Ball: %@", ball);
    ...

返回此崩溃:

-[PKPhysicsContact bodiesMatchingCategory:]: unrecognized selector sent to instance 0x17dad9e0
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[PKPhysicsContact bodiesMatchingCategory:]: unrecognized selector sent to instance 0x17dad9e0'

---

添加了Apple的Bug Report,#23332190

Answer 1

我用这个简单的代码得到了同样的错误:

extension SKPhysicsContact {
    func bodiesMatchingCategory(mask: UInt32) -> [SKPhysicsBody] {
        let bodies = [bodyA, bodyB]
        return bodies.filter { ($0.categoryBitMask & mask) != 0 }
    }
}

let contact = SKPhysicsContact()
let body = contact.bodiesMatchingCategory(0)

问题是,即使你明确地告诉它是一个,并且扩展已经开启,你的注意类型contact是PKPhysicsContact(正如你所注意到的).您必须能够进行扩展才能使其正常工作.从这个逻辑来看,我们可以说目前没有任何实例方法可以在扩展中工作.我说这是SpriteKit的一个错误,你应该提交雷达.类方法仍然有效,因为您在类本身上调用它们.SKPhysicsContactSKPhysicsContactPKPhysicsContactSKPhysicsContact

在此期间,您应该能够将该方法移动到场景或其他对象中并成功调用它.

为了记录,这不是特定于Swift的问题.如果在Objective-C类别中使用相同的方法,SKPhysicsContact则会发生相同的崩溃.