KentarouKanno/Associated Objects.md

## Associated Objects.md

      
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              Associated Objects.md
            
          
    Associated Objects

★ 既存のクラスに新たにプロパティを追加する
class MyObject: NSObject {}

private var key = 0

extension MyObject {
    var str:String {
        get {
            return objc_getAssociatedObject(self, &key) as! String
        }
        set {
            objc_setAssociatedObject(self, &key, newValue, objc_AssociationPolicy.OBJC_ASSOCIATION_COPY_NONATOMIC)
        }
    }
}