Thread: Reading data from a text file

I am using this struct to store data from a text file

Code:

struct sItem
{
    short unsigned int  Number;
    sDate Date;
    std::string Name;
    std::string Memo;
    std::string MainCatagory;
    std::string SubCatagory;
    long double Amount;
    std::string Type;
};

the file uses tags to determine what data member each line belongs to like this : (CODE_TAG)(DATA)

Code:

<STMTTRN>
<TRNTYPE>DTSF
<DTPOSTED>20080331
<TRNAMT>1211.65
<NAME>SUBDT-TR
<MEMO>8105T
</STMTTRN>

Each line in the file is saved to a std::string and the tag is extracted to determine which data member the line should be saved to.

Code:

do {
    read line into std::string temp;
    extract first part of line into std::string Code_Tag;
    extract the rest of the line into std::string Data;
    using Code_Tag, determine what Data is and save it to the approperiate sItem member;
} while (NOT EOF)

I'm just not sure of the best method to do this. I could use a bunch of if...then statements like this

Code:

if (Code_Tag == "TRNTYPE") Item.Type = data;
if (Code_Tag == "NAME") Item.Name = data;
...

But I don't like the way that looks, and it seems like there would be too much over head with all the 'if...then' tests.

I could use a switch...case statement but VC Toolkit 2003 will not let me switch a std::string.

I have also tried enumerating the code tags like this

Code:

typedef enum CODE_TAGS
{
    TAG_START      = 0xff01,
    TAG_TYPE       = 0xff02,
    TAG_DATE       = 0xff03,
    TAG_AMOUNT     = 0xff04,
    TAG_NAME       = 0xff05,
    TAG_MEMO       = 0xff06,
    TAG_ITEMNUM    = 0xff07,
    TAG_END        = 0xff08
};

and just switching that, but then I have to convert each line from the std::string to the enum value. This seems to be just as much of a pain as the first idea.

Any thoughts / ideas on what the best way would be to go about doing this?

A switch must have a constant condition - something that can be evaluated at compile time. Therefore, a std::string cannot be switched.
One approach to this is to use a map. The std::string as key, and a pointer to your data as value.

Originally Posted by Daved

It gets a little more complicated since you are also storing shorts, doubles, and dates, though.

Although not impossible and quite easy with polymorphism and generic coding. I would find it an interesting challenge.
If you feel up to it, that is.

The map idea is interesting. I have not delt a whole lot with maps so I may have to look into that. May be worth the challenge.

I am not actually using EOF, the last line of the text file will have a tag that notes the end of file. That is what I am using to break out of the do...while loop. Although, I think that eventually I will have to abandon that idea and go to a more traditional EOF control

Well, I guess our ways differ. Both certainly are possible, but as far as I see, using the polymorphic approach allows for more generic code.
No need to keep adding different maps.
Hmmm. Boost::variant, though... Isn't that just to store all different types inside one map and then try to query and guess the correct type and delegate it correctly? Somehow, I don't find that a very promising solution, unless you have a better way that I can't think of right now.

Originally Posted by Daved

Polymorphism (and probably boost::variant, too) is much too complex of a solution for such a simple task.

Unless it turns into something bigger, I agree.