在 SpriteKit 中检查节点和实例类型之间的冲突答案

【问题标题】：Checking for collision between a node and a instancetype in SpriteKit在 SpriteKit 中检查节点和实例类型之间的冲突
【发布时间】：2014-07-02 22:18:14
【问题描述】：

我正在尝试在我的游戏中测试子弹和特定类型的砖块之间的碰撞，这是一个 Brick Breaker 类型的游戏。当子弹击中砖块时，砖块就会被移除。我可以测试任何砖块和子弹之间的碰撞，并将它们移除。但我无法让特定类型的砖块之间发生碰撞，然后移除该砖块。

这是我的 Brick.h 类

#import <SpriteKit/SpriteKit.h>

typedef enum : NSUInteger {
    // Normal Bricks
    Blue = 1,
    LightBlue = 2,
    DarkBlue = 3,
    Green = 4,
    LightGreen = 5,
    DarkGreen = 6,
    Grey = 7,
    DarkGrey = 8,
    Pink = 9,
    LightPink = 10,
    Purple = 11,
    LightPurple = 12,
    DarkPurple = 13,
    Red = 14,
    DarkRed = 15,
    Orange = 16,
    Gold = 17,
    Yellow = 18,
    Teal = 19,
    Brown = 20,
} BrickType;

static const uint32_t BRICK_CATEGORY = 0x1 << 2;

@interface XSBrick : SKSpriteNode

@property (nonatomic) BrickType type;
@property (nonatomic) BOOL indestructible;
@property (nonatomic) BOOL spawnsExtraBall;
@property (nonatomic) BOOL givesExtraLife;
@property (nonatomic) BOOL enlargePaddle;
@property (nonatomic) BOOL spawnsTwoOrThreeExtraBalls;
@property (nonatomic) BOOL makesBallSlow;
@property (nonatomic) BOOL makesBallFast;
@property (nonatomic) BOOL bullets;

-(instancetype)initWithType:(BrickType)type;
-(void)hit;

@end

Brick.m 类

#import "XSBrick.h"

@implementation XSBrick
{
    SKAction *_brickSmashSound;
}

#pragma mark - Load Bricks
-(instancetype)initWithType:(BrickType)type
{
    switch (type) {
        // Normal Bricks
        case Blue:
            self = [super initWithImageNamed:@"BrickBlue"];
            break;

        case LightBlue:
            self = [super initWithImageNamed:@"BrickLightBlue"];
            break;

        case DarkBlue:
            self = [super initWithImageNamed:@"BrickDarkBlue"];
            break;

        case Green:
            self = [super initWithImageNamed:@"BrickGreen"];
            break;

        case DarkGreen:
            self = [super initWithImageNamed:@"BrickDarkGreen"];
            break;

        case LightGreen:
            self = [super initWithImageNamed:@"BrickLightGreen"];
            break;

        case Grey:
            self = [super initWithImageNamed:@"BrickGrey"];
            break;

        case DarkGrey:
            self = [super initWithImageNamed:@"BrickDarkGrey"];
            break;

        case Pink:
            self = [super initWithImageNamed:@"BrickPink"];
            break;

        case LightPink:
            self = [super initWithImageNamed:@"BrickLightPink"];
            break;

        case Purple:
            self = [super initWithImageNamed:@"BrickPurple"];
            break;

        case LightPurple:
            self = [super initWithImageNamed:@"BrickLightPurple"];
            break;

        case DarkPurple:
            self = [super initWithImageNamed:@"BrickDarkPurple"];
            break;

        case Red:
            self = [super initWithImageNamed:@"BrickRed"];
            break;

        case DarkRed:
            self = [super initWithImageNamed:@"BrickDarkRed"];
            break;

        case Orange:
            self = [super initWithImageNamed:@"BrickOrange"];
            break;

        case Gold:
            self = [super initWithImageNamed:@"BrickGold"];
            break;

        case Yellow:
            self = [super initWithImageNamed:@"BrickYellow"];
            break;

        case Teal:
            self = [super initWithImageNamed:@"BrickTeal"];
            break;

        case Brown:
            self = [super initWithImageNamed:@"BrickBrown"];
            break;

        default:
            self = nil;
            break;
    }

    return self;
}

在 MyScene.m 中，didBeginContact。这可行，但会移除子弹击中的任何类型的砖块

// Collision between bullets and bricks
    if (firstBody.categoryBitMask == BRICK_CATEGORY && secondBody.categoryBitMask == BULLET_CATEGORY) {
        [firstBody.node removeFromParent];
        [secondBody.node removeFromParent];
    }

我已经尝试过了，但是 Xcode 给了我一个 SKNode 和 NSUInteger 之间比较的警告，所以它不起作用。

// Collision between bullets and bricks
    if (firstBody.categoryBitMask == BRICK_CATEGORY && secondBody.categoryBitMask == BULLET_CATEGORY) {
        if (firstBody.node == LightBlue) {
            [firstBody.node removeFromParent];
        }
        [secondBody.node removeFromParent];
    }

我也尝试过创建我的 Brick 实例，然后对其进行测试，但这也不起作用。

// Collision between bullets and bricks
    if (firstBody.categoryBitMask == BRICK_CATEGORY && secondBody.categoryBitMask == BULLET_CATEGORY) {
        XSBrick *LightBlueBrick = [[XSBrick alloc]initWithType:LightBlue];
        if (firstBody.node == LightBlueBrick) {
            [firstBody.node removeFromParent];
        }
        [secondBody.node removeFromParent];
    }

我在这方面已经有一段时间了，现在试图让它发挥作用。另外，我对 iOS 开发还是很陌生，因此我们将不胜感激。

编辑：

我试过你的答案，rickster，但它抛出了一个错误，“2014-07-02 09:13:52.527 Brick Breaker[44129:60b] -[SKSpriteNode type]: unrecognized selector sent to instance 0x12145a2a0”。但我确实使用您提供的一些代码让它工作。

// Collision between bullets and bricks
if (firstBody.categoryBitMask == BRICK_CATEGORY && secondBody.categoryBitMask == BULLET_CATEGORY) {
    XSBrick *brick = nil;
    SKNode *bullets = nil;
    if ([firstBody.node isKindOfClass:[XSBrick class]]) {
        brick = firstBody.node;
        bullets = secondBody.node;
        if (brick.type == LightBlue) {
            [firstBody.node removeFromParent];
        }
        else if (brick.type == Blue) {
            [firstBody.node removeFromParent];
        }
    }
    [secondBody.node removeFromParent];
}

现在可以了。它检测击中的砖块类型，然后移除该砖块。如果它不在我的 if 语句中，它不会被删除，这正是我想要的方式。非常感谢您的帮助！！

【问题讨论】：

firstBody.node.type == LightBlue

标签： ios sprite-kit collision

【解决方案1】：

if (firstBody.node == LightBlue) 不起作用，因为您将节点（对象指针）与枚举值（整数）进行比较。您需要比较相同类型的值以使相等比较具有任何有用的含义。

if (firstBody.node == LightBlueBrick) 不起作用，因为您正在针对您在此处创建的 XSBrick 实例进行测试。您已经在didBeginContact 中，所以有一个已经存在的节点参与了冲突——如果您创建一个新节点，则保证该节点不是已经存在的节点。您只需要检查碰撞中每个节点的属性即可找出它是哪个节点或哪种节点。

您已经有一个if 语句来测试firstBody.categoryBitMask 是否与您用于积木的值相匹配。如果您确定您仅将该值用于积木，您可以放心地假设firstBody.node 指向XSBrick 的一个实例。（不过，安全的做法是使用isKindOfClass。）

为了让编译器让您调用XSBrick 方法，您需要将firstBody.node 转换为该类类型。然后您可以检查您在XSBrick 上定义的type 属性。

最后，SpriteKit 不保证接触处理程序中物体的顺序，因此砖块和子弹碰撞中的第一个物体不一定是砖块。

这些是您解决此问题所需的要素。将它们放在一起，这是您的联系人处理程序的示例实现：

- (void)didBeginContact:(SKPhysicsContact *)contact {
    // If we expect more than one kind of collision, check that first
    if (contact.bodyA.categoryBitMask | contact.bodyA.categoryBitMask == BRICK_CATEGORY | BULLET_CATEGORY)
        // We know it's a brick/bullet collision, sort out which body is which
        XSBrick *brick = nil;
        SKNode *bullet = nil;
        if ([contact.bodyA.node isKindOfClass:[XSBrick class]]) {
            brick = contact.bodyA.node;
            bullet = contact.bodyB.node;
        } else  {
            brick = contact.bodyB.node;
            bullet = contact.bodyA.node;
        }

        // Now, check the type of brick
        if (brick.type == LightBlue) {
            // Do whatever with light blue bricks
        } else {
            // Do whatever with other kinds of bricks
        }
    }
}

【讨论】：