Question

在我的应用程序中，我试图访问数组值，但数组返回零值。我现在已经坚持了几个小时，似乎无法解决它。所以任何帮助将不胜感激：

@implementation MyScene{
 NSMutableArray *_touchPoints;
}

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    CGPoint touchPoint = [[touches anyObject] locationInNode:self.scene];
    [self clearTouchPoints];
    [self addTouchPointToMove:touchPoint];
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    CGPoint touchPoint = [[touches anyObject] locationInNode:self.scene];
    CGPoint targetPoint = CGPointMake(touchPoint.x , touchPoint.y - delta.y);
    [self addTouchPointToMove:touchPoint];
    NSLog(@"Value: %lf", touchPoint.y);
}

- (void)move:(NSNumber *)_tempTime{
    CGPoint currentPoint = [_touchPoints[0] CGPointValue];
    CGPoint targetPoint = [_touchPoints[1] CGPointValue];
    NSLog(@"Check Value: %lf", targetPoint.y);
}

- (void)addTouchPointToMove:(CGPoint)point {
   [_touchPoints addObject:[NSValue valueWithCGPoint:point]];
}

- (void)clearTouchPoints {
   [_touchPoints removeAllObjects];
}

Answer 1

数组永远不会被初始化（例如，_touchPoints = [NSMutableArray new];），因此它是nil。试图在nil对象上调用方法什么也不做，也没有抱怨（即不抛出异常）。所以在addTouchPointToMove方法中：

[_touchPoints addObject:[NSValue valueWithCGPoint:point]];

什么也没做。

在init方法中，初始化数组。

在其他实例中访问数组值

1 个答案: