控制台有报错，[Vue warn]: Error in callback for watcher "function () { return this._data.$$state }": "Error: [vuex] do not mutate vuex store state outside mutation handlers."

[xiongxiaocui]

trafficstars

[Vue warn]: Error in callback for watcher "function () { return this._data.$$state }": "Error: [vuex] do not mutate vuex store state outside mutation handlers."

[Charming2015]

请问是怎么使用的？我应该怎样重现这个问题？