将自定义属性添加到SKNode并将其与'enumerateChildNodesWithName：usingBlock：'结合使用

Question

What I wish to do is: to extend SKNode with a custom property, a plain int, and later use it with enumerateChildNodesWithName:usingBlock: .

Since I am a total beginner I failed to understand tutorials of how to do this with the 'userData' property of SKNode. I also attempted to create a subclass of NSObject/SKNode and adding the property there. But then I failed to make it work with enumerateChildNodesWithName:usingBlock: .

Extending SKNode seemed more straight forward to me.

the compiler does not complain about the following code:

SKNode_weight.h

  @interface SKNode ()
  @property int weight;
  @end

MyScene.h

  #import "SKNode_weight.h"

MyScene.m

  #import "MyScene.h"
  #import "SKNode_weight.h"

  @implementation MyScene

  -(void) spawnBall {      
      SKNode *ballNode = [SKNode node];
      ballNode.weight = 10; // fixed value for simplicity
      ballNode.name = @"ball";

      [self addChild:ballNode];
  }

  -(id)initWithSize:(CGSize)size {
      if (self = [super initWithSize:size]) {
          [self spawnBall];
      }
      return self;
  }

  -(void) sumWeight{
        [self enumerateChildNodesWithName:@"ball" usingBlock:^(SKNode *node, BOOL *stop) {
              NSLog(@"%i", node.weight);
        }];
  }
    @end

the build is successful, but I get the following error:

-[SKNode setWeight:]: unrecognised selector sent to instance 0x96328f0

I hope somebody can give a an example of a quick and painless solution. Thank you, Flo

Answer 1

It is not possible to add members and properties to an existing class via a category — only methods.

http://developer.apple.com/library/ios/#documentation/General/Conceptual/DevPedia-CocoaCore/Category.html

Best way would be to subclass SKNode and add weight property to the subclass.

SKNodeWeighted.h

@interface SKNodeWeighted : SKNode

    @property int weight;

@end

Then use it like you would use the category with slight differences.

 #import "MyScene.h"
 #import "SKNodeWeighted.h"

  @implementation MyScene

  -(void) spawnBall {      
      SKNodeWeighted *ballNode = [SKNodeWeighted node];
      ballNode.weight = 10; // fixed value for simplicity
      ballNode.name = @"ball";

      [self addChild:ballNode];
  }

  -(id)initWithSize:(CGSize)size {
      if (self = [super initWithSize:size]) {
          [self spawnBall];
      }
      return self;
  }

  -(void) sumWeight{
        [self enumerateChildNodesWithName:@"ball" usingBlock:^(SKNode *node, BOOL *stop) {
              if ([node isKindOfClass:[SKNodeWeighted class]])                   {
                  NSLog(@"%i", ((SKNodeWeighted*)node).weight);
              } 
        }];
  }
  @end