我想获取核心数据属性的值，在获取此对象/值后我想更新它。这是我的代码:varnumberOfChanges:Int32?numberOfChanges=theme.valueForKey("numberThemeChanged")asInt32varnewValueThemeChanges:Int32?newValueThemeChanges=numberOfChanges+1theme.setValue(newValueThemeChanges,forKey:"numberThemeChanged")我收到以下错误:Type'Int32'doesnotconformtoprotoco