Okay, time for another code post. Prompted by a comment on an earlier post about Merb and MYOB, I thought I’d provide some more detail on how to talk to MYOB using Ruby, for any other people stuck in a similar position.

ODBC Bindings

If you like crafting your own SQL, this is the easiest approach. Firstly, you’ll need to download Christian Werner’s ODBC Bindings for Ruby, and install it using the following commands (or something along these lines) from within the source directory:

ruby extconf.rb
make
sudo make install

Documentation is a bit light on examples - and it’s really just a hook into the C libraries for ODBC, so good luck reading the source. Here’s some of the basic things you’ll need to do. (Don’t forget to require 'odbc' first, of course).

Setting up a Connection

You can either go through the DSN collection, or connect using the string name of the DSN (which in this case we’ll assume is ‘MYOB’):

dsn = ODBC.datasources.detect { |source| source.name == "MYOB" }
database = ODBC::Database.connect dsn

# or

database = ODBC::Database.connect "MYOB"

Note that the ODBC.datasources collection only contains system DSNs, not User-level ones. Not sure why, or how to access the latter.

SELECT Statements

statement = database.prepare "SELECT * FROM Customers"
statement.execute
statement.each_hash d |row|
  # results accessed as row["column_name"]
end
statement.drop

Make sure you drop the statement once you’re done with it, otherwise you’ll get complaints when you stop ruby that the statements weren’t all closed and dropped.

There’s other ways to access results - you can go through results as you see fit using fetch or fetch_hash, depending on whether you want an array or hash of the record.

INSERT Statements

With other SQL statements (although there’s no use of UPDATE or DEETE in MYOB connections), you don’t really care about the results, so that makes things a bit simpler, you can just call database.do("INSERT INTO Import_Customer_Cards (...) VALUES (...)"). The do method creates the statement, executes it and then drops it for you. MYOB makes this a little more complex though, as it all must be done in transactions - not that that’s a bad thing.

database.transaction do |env|
  env.do("INSERT INTO Import_Customer_Cards (...) VALUES (...)")
end

This won’t actually do anything though - and it won’t throw up an error or warning. The problem is you need to turn autocommit mode off, because the MYOB ODBC drivers don’t like it (it’s not a problem with Christian’s bindings). So, back when you create your connection:

database = ODBC::Database.connect "MYOB"
database.autocommit = false

ActiveRecord

If you prefer some level of abstraction above the messy SQL, then it might be worth looking at OpenLink’s ActiveRecord ODBCAdapter. I recommend the gem instead of the plugin, as the plugin takes it upon itself to modify your code, which I don’t like.

sudo gem install odbc-rails

Now, I’m not an ODBC expert, but there seems to be different flavours of ODBC connections possible - and MYOB’s is not one supported by this gem. So, if you’re using Rails, put the gem into vendor (and for Merb, into the local gems folder), then modify it with this patch. I make no promises for it being stable or reliable - but I’ve not had any problems yet.

Of course, using ActiveRecord is viable if you’re just reading data out

• but if you want to write as well as read, then there’s issues. MYOB has separate write tables (prefixed with ‘Import_’), and they have denormalised schemas compared to the read-equivalents.

For database.yml, you’ll need something like the following:

development:
  adapter: odbc
  dsn: MYOB

Everything Else

In both the situations above, I’ve not put usernames or passwords into the connections - you can, but that is already handled by the ODBC DSN, so I keep my code that bit simpler.

For those who are new to coding for MYOB - it does cost money to get a developer account (several hundred dollars per year), which is the only way to get write access. I think read access is a once off fee of a couple of hundred dollars, but that’s specific to a MYOB file.

And if anyone is wondering - while I was initially using the odbc-rails library, I’ve now switched to constructing the SQL myself and just using the bindings, because of the table issues.