搜尋子字串

要搜尋 String 是否包含子字串，請執行以下操作：

NSString *myString = @"This is for checking substrings";
NSString *subString = @"checking"; 

BOOL doesContainSubstring = [myString containsString:subString];  // YES

如果定位到 iOS 7 或 OS X 10.9（或更早版本）：

BOOL doesContainSubstring = ([myString rangeOfString:subString].location != NSNotFound);  // YES