类型转换

hechengjin

set view(value) {
  value instanceof Ci.nsIMsgDBView;
  let totalMessages = value.db.folder.getTotalMessages(false);
  console.log('TreeView.js set view',totalMessages, value) //[info] TreeView.js set view 1 [xpconnect wrapped (nsISupports, nsIMsgDBView, nsITreeView)]
}

1. aEvent instanceof Ci.nsIDragSession
   
2.     let messenger = Cc['@mozilla.org/messenger;1'].createInstance(Ci.nsIMessenger)

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