- (void)viewDidLoad {

    [super viewDidLoad];

    NSString *str1 = @"<hello,wo  r d!>";

    //删除字符串两端的尖括号

    NSMutableString *mString = [NSMutableString stringWithString:str1];

    //第一个参数是要删除的字符的索引，第二个是从此位开始要删除的位数

    [mString deleteCharactersInRange:NSMakeRange(0, 1)];

    [mString deleteCharactersInRange:NSMakeRange(mString.length-1, 1)];

    NSLog(@"mString:%@",mString);

    //删除字符串中的空格

    NSString *str2 = [mString stringByReplacingOccurrencesOfString:@" " withString:@""];

    NSLog(@"str2:%@",str2);

    //同样的可以替换字符

    NSString *str3 = [str2 stringByReplacingOccurrencesOfString:@"," withString:@"好"];

    NSLog(@"str3:%@",str3);

    //替换某一位置的字符

    NSString *str4 = [str3 stringByReplacingCharactersInRange:NSMakeRange(0, 1) withString:@"哈哈"];

    NSLog(@"str4:%@",str4);

}