ios開發答疑錄系列​—(五)NSString 和NSCharacterset的不同之處

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An NSString object represents a string of ordered characters (text). An NSCharacterSet object represents a set of characters in no particular order. It is often much quicker to determine whether a character is a member of an NSCharacterSet than an NSString. You can't use an NSCharacterSet object to hold text, at least not in any sensible way, because it does not maintain any order of characters, its use is primarily for determining whether a character exists in a set of characters.

我們在nsstring的分割，尋找等操作中，經常會提供兩種函數，參數類型分別為NSString 和NSCharacterset，有什麼不同呢？

NSString 是有序字串

NSCharacterset是無需字元集合，主要用來判斷已知字串是否包含制定字元集，而不可以用來儲存字串。