1.字串中是否包含a

Bool is=[cityModel.name containsString:@"a"];

2.轉換成小寫

NSString *str = [NSString stringWithFormat:@"%@",@"AA"].lowercaseString;

3. a在str1中的位置(location)及a的長度(length)

NSRange *range=[str1  rangeOfString:@"a"];

4.//去除換行字元

        text = [text stringByTrimmingCharactersInSet:[NSCharacterSet

5.將日期轉換成字串

    NSString *nowDateStr = [fmt stringFromDate:nowDate];