@interface for 'UIAttachmentBehavior' declares the selector 'initWithItem:point:attachedToAnchor:'

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In Chapter2 Attaching Multiple Dynamic Items to Each Other
self.attachmentBehavior = [[UIAttachmentBehavior alloc]
initWithItem:self.squareView
point:self.squareViewAnchorView.center
attachedToAnchor:self.anchorView.center];

No visible @interface for 'UIAttachmentBehavior' declares the selector 'initWithItem:point:attachedToAnchor:'

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fix "No visible @interface for 'UIAttachmentBehavior' declares the selector 'initWithItem:point:attachedToAnchor:'"
UIOffset offset = UIOffsetMake(self.squareViewAnchorView.center.x, self.squareViewAnchorView.center.y);
self.attachmentBehavior = [[UIAttachmentBehavior alloc] initWithItem:self.squareView
offsetFromCenter:offset
attachedToAnchor:self.anchorView.center];