Programming: April 2006 Archives

Ruby on Rails is the most recently hyped language, so I though about testing it out on my development server. I followed the tutorial available on the RoR website. It went fine until I did a ./scripts/generate command and got lot of syntax errrors:

/usr/lib/ruby/1.8/yaml.rb:133:in `load': syntax error on line 27, col 2: `  host: localhost' (ArgumentError)
 from /usr/lib/ruby/gems/1.8/gems/rails-1.1.2/lib/initializer.rb:459:in `database_configuration'
        from /usr/lib/ruby/gems/1.8/gems/rails-1.1.2/lib/initializer.rb:181:in `initialize_database'
        from /usr/lib/ruby/gems/1.8/gems/rails-1.1.2/lib/initializer.rb:84:in `process'
        from /usr/lib/ruby/gems/1.8/gems/rails-1.1.2/lib/initializer.rb:42:in `run'
        from ../config/../config/environment.rb:13
        from /usr/lib/site_ruby/1.8/rubygems/custom_require.rb:21:in `require'
        from /usr/lib/ruby/gems/1.8/gems/activesupport-1.3.1/lib/active_support/dependencies.rb:147:in `require'
        from /usr/lib/ruby/gems/1.8/gems/rails-1.1.2/lib/commands/generate.rb:1
        from /usr/lib/site_ruby/1.8/rubygems/custom_require.rb:21:in `require'
        from /usr/lib/ruby/gems/1.8/gems/activesupport-1.3.1/lib/active_support/ 

I started looking around at the folder structure that Ruby installs itself into when you create a new RoR application. Below my main folder, which the tutorial instructed my to create an alias or virtual directory for is the config folder. Inside the config folder is the database.yml file, holding my database information, with accounts and hard-coded passwords. (On my box, it's all localhost only, but still...)

Just to check, I fired up my browser and entered http://myserver/myrailsalias/config/database.yml. All the information popped up. I changed the Apache alias to /mypathtorails/public/ which I didn't see in the tutorial. This seems to be a lot more secure. This doesn't mean RoR is any more or less secure than any other interpreted scripting language for web applications, just that right now, it's easy to install it in a less secure manner.

What's the point? Know what you're installing, where it installs, what permissions it needs, and what context it runs as. And don't put your database.yml someplace where anyone can download it. I know there are websites where I could find it, but I'm not going to try. That doesn't mean someone else isn't writing a bot to find it right now.

Oh, and know how Apache works and httpd.conf works, too. All that is a lot to expect for people looking for a simple programming language.

For a grad school project we need to build a system that bills people by the amount of time they rent a car. Thus, I needed to use the DateDiff function of VB and SQL in Access. I looked it up using Access help and got to the right MSDN page:

Syntax

DateDiff(interval, date1, date2[, firstdayofweek[, firstweekofyear]])

They tell you that interval is a String and link to what a string is. The part they don't say explicitly is that you need to enclose the interval value in quotation marks. "Of course," you say, "It's a string." Is it too much to ask for an example showing it in use with the quotation marks? e.g.

In Microsoft Access:
WHERE (((Rentals.CarOut)=True)) AND ((DateDiff("h",Rentals.DropOffDate,Now())>3));
In Microsoft SQL: (Transact-SQL for SQL 2000/2005)
WHERE (((Rentals.CarOut)=True)) AND ((DateDiff("h",Rentals.DropOffDate,GETDATE())>3));

Where h is the code for hours.

I just wanted to write this down someplace before I forget it. And why must Access and T-SQL be different? Now() doesn't work in T-SQL and GETDATE() doesn't work in Access.

When you switch languages a couple of times a day, you begin to confuse some syntax and notice differences between the languages. In one week: get basketball tournament application working again. (PHP) Get Java app connected to Derby open-source database for my Java class (handed in to my professor before class meets, but implemented in a class). Get VB (6, not .net) apps working for Decision Support Systems class (targeting zip codes) and Databases class (rental car system). Get VBscript flight-risk scoring system working. While Visual Basic and VB Script are close, they’re not the same. You can dim intX as int in VB, but you can only dim intX in VB Script.  (The again, my server doesn’t even let me do option explicit: The specified 'option explicit ' option is unknown or invalid.)

And while you can do a Adodc.recordset.recordsize in VB6, Java (1.5) has no resultSet.recordsize. So when I do a query in VB using ADO, I know how many records I have; but in Java, I have to do while(recordset.next()) { recount++} (source). So my obsolete version of VB knows how many records are in my set, but the latest version of Java does not. I’m sure there’s a reason for this, I just don’t know what it is. I haven’t figured out if there’s a recordset size() function/method in PHP yet. I wonder if Ruby on Rails has one available – I’d check but the RoR API documentation isn’t searchable.