NSString 去空白字符

去除字符串左右两边的空白是比较通用的代码逻辑：

@interface NSString (Strip)

- (NSString *)wbt_trimmedString;
- (NSString *)wbt_leftTrimmedString;
- (NSString *)wbt_rightTrimmedString;

@end

@implementation NSString (Strip)

/* Returns a new string made by removing from start of the receiver whitespace and newline characters */
- (NSString *)wbt_leftTrimmedString
{
    NSRange range = [self rangeOfCharacterFromSet:[NSCharacterSet whitespaceAndNewlineCharacterSet].invertedSet];

    return [self substringFromIndex:range.location];
}

/* Returns a new string made by removing from end of the receiver whitespace and newline characters */
- (NSString *)wbt_rightTrimmedString
{
    NSRange range = [self rangeOfCharacterFromSet:[NSCharacterSet whitespaceAndNewlineCharacterSet].invertedSet options:NSBackwardsSearch];
    
    return [self substringToIndex:range.location];
}

/* Returns a new string made by removing from both ends of the receiver whitespace and newline characters */
- (NSString *)wbt_trimmedString
{
    return [self stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
}

@end