iOS NSUserDefaults数据保存报错：Attempt to set a non-property-list object...

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在使用NSUserDefaults的时候插入数据有时候会报以下错误：

Attempt to set a non-property-list object <CFBasicHash 0x7f9c1a5cce80 [0x11192c7b0]>{type = immutable dict, count = 27,
entries =>
	3 : ext_attr = <CFString 0x110446380 [0x11192c7b0]>{contents = ""}
	4 : zhicheng = <CFString 0x110446380 [0x11192c7b0]>{contents = ""}
	5 : code = <CFString 0x7f9c1a54e900 [0x11192c7b0]>{contents = "YS1000000000011"}
	6 : zhuzhi = <CFString 0x110446380 [0x11192c7b0]>{contents = ""}
	10 : sex = <CFString 0x110446380 [0x11192c7b0]>{contents = ""}
	14 : cat_id = <CFString 0x110446380 [0x11192c7b0]>{contents = ""}
	15 : pass = 123123
	16 : keshi = <CFNull 0x11192caf0 [0x11192c7b0]>
	18 : name = <CFString 0x7f9c1a566740 [0x11192c7b0]>{contents = "新医生"}
	19 : sp = <CFString 0x110446380 [0x11192c7b0]>{contents = ""}
	20 : moreinfo = <CFString 0x110446380 [0x11192c7b0]>{contents = ""}
	21 : state = <CFString 0x110446380 [0x11192c7b0]>{contents = ""}
	22 : <CFString 0x7f9c1a564dc0 [0x11192c7b0]>{contents = "comment_num"} = 0
	23 : id = 11
	25 : p_attr = <CFString 0x110446380 [0x11192c7b0]>{contents = ""}
	26 : pcolumn = 1
	27 : pic = <CFString 0x7f9c1a56d330 [0x11192c7b0]>{contents = "http://58.61.37.228:3080/td_yisheng/static/img/photo.gif"}
	28 : <CFString 0x7f9c1a5165f0 [0x11192c7b0]>{contents = "zhizhaopic"} = <CFString 0x110446380 [0x11192c7b0]>{contents = ""}
	29 : mobile = <CFString 0x7f9c1c8f8ee0 [0x11192c7b0]>{contents = "18682355562"}
	30 : showtpl = 1
	31 : email = <CFString 0x110446380 [0x11192c7b0]>{contents = ""}
	32 : area = <CFString 0x7f9c1c8f3ba0 [0x11192c7b0]>{contents = "区域"}
	33 : uptime = <CFArray 0x7f9c1a5ceff0 [0x11192c7b0]>{type = immutable, count = 1, values = (
	0 : <CFString 0x110446380 [0x11192c7b0]>{contents = ""}
)}
	36 : price = <CFBasicHash 0x7f9c1c8e3080 [0x11192c7b0]>{type = immutable dict, count = 5,
entries =>
	2 : baoyue = 1
	3 : dianhua = 1
	4 : huizhen = 1
	5 : yuyue = 1
	6 : zixun = 1
}

	38 : <CFString 0x7f9c1c8e2c60 [0x11192c7b0]>{contents = "comment_rank"} = 5
	39 : regtime = <CFString 0x7f9c1c8fb2b0 [0x11192c7b0]>{contents = "1442394762"}
	40 : patchcode = <CFString 0x110446380 [0x11192c7b0]>{contents = ""}
}
 as an NSUserDefaults/CFPreferences value for key UserModelDic

自定义的类型需要转成NSData再存入。

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我原来认为NSUserDefaults存不了数组，又换成了字典，但是还是报错，最后求助网友大神解决了，是我里边的数据结构有"<null>"，而NSUserDefaults是不能被成功解析并存入的，所有在存入之前需要将里边的"<null>"改成""即可。