Class or Dictionary

Getting Started
1

Hello,

I’m trying to read a rather large XML file with tons of fields.
I can read the file properly but I’m stuck finding the right way to store and then later work with the key/values.

To keep it simple, let’s say the structure is something like a collection of persons:

name - value
address - value
zip - value
city - value
country - value
phone - value

However, instead of 6, there are 50+ fields and 20 or 30 ‘persons’ per file.

Because there are so many fields, I would like to use a dictionary and instead of setting the key to ‘John Smith’, i prefer to set it to ‘name’ (the XML node name). That’s fine with one person but I don’t see how that’s supposed to work with multiple.

So on to a class. With a class, I can do appends but I also need to pre-define all fields.

2 questions:

  • When going with a dictionary, what would the best way be? Multidimensional? How does that work? Or putting them in an array (if possible) where the key is some kind of ID? But if I do that, I think I lose the benefit of dictionaries and their fast lookups.

  • With a Class where all the properties are pre-defined, is it possible to somehow dynamically fill in the property name when assigning values to it? (something like myClass.xmlNodeName where xmlNodeName is a variable?) If that’s not possible, how’s that normally done? Going through a large Select Case when parsing the XML?

This is most likely a ver basic question but I’m trying to learn. A pointer in the right direction would be very welcome. :slight_smile:

2

What about a class that internally just uses a dictionary

And each instance represents one Person

That way you can have an array of these and they can, on a per person basis, have differing numbers of “fields” each accessed by the name of the field (from the XML)

3

You want to do BOTH.

Create a class that describes ONE instance of the data
then create a DICTIONARY that contains multiple instances of the class.

OR… the better approach… create and use an SQLite Database

4

the only difficulty with creating a class is, without a priori knowledge of what fields ARE in every xml file for each person, you might need to be extra flexible & handle them in whatever form they come in

I’d agree that NORMALLY you want to have a representation that would map to a class or that you can represent in a sql table / db

sometimes you do need the flexibility of a class that has an indefinite list of “properties” that you can access “by name”

operator_lookup is really handy for this kind of case

5

I never heard of operator_lookup before. Very interesting.
In this case, the fields are known. It’s just more work to map things correctly. The Dictionary approach looked so much simpler and cleaner.
Thanks!

6

Interesting, yes, but I’d caution against it. The compiler can’t help you if you use the ‘wrong’ name because the member lookup just turns into a call to Operator_Lookup at runtime.

7

If you know the structure of the XML file and it is well defined, create a class to represent your data. Only use a dictionary if you are working with a structure that changes frequently and you only need access to a few fields that you know are “stable” in their definition. Creating a class gives you all the benefit of the compiler and IDE. For example, when using a dictionary you could do:

Print dict.Value("FirstName")
// Later in Code
dict.Value("FirsName") = "Jim"

Notice the slight typo. If however you had a class, you would get IDE completion of FirstName and if you did misspell it a compiler error. Further, you will get real types. For example, FirstName as String, BirthDate as Date, Age as Integer, etc…

It’s a little work at the start but I believe the benefits far outweigh the work, especially if this is an app that is going to stay around for a while. Maybe a one time data conversion or something I wouldn’t go through the trouble, but anything more than that… go through the trouble.