PullMonkey Blog

Headers and Footers in ruby’s Spreadsheet gem

Have you ever needed to add a header or footer to your spreadsheets in ruby?
Yah, well, we have
Yes, you can do this with the Write Excel gem.
But we've already written years worth of spreadsheet code with the spreadsheet gem and don't want to rewrite it all.

Anyway, we thought we'd share our little trick to get page headers using the spreadsheet gem.

So what you see here (above) goes into a config/initializer, something like RAILS_ROOT/config/initializer/enable_headers_in_spreadsheet_gem.rb. Here's what's going on:

1) We know that the write_from_scratch method is called when everything is said and done and the data is ready to be written to the spreadsheet file. So we make use of this and alias that method to write_from_scratch_without_header. Which opens us up to call our write_header method inside our write_from_scratch method which, of course, will call the original write_from_scratch method.

2) Our write_header method makes use of the already existing opcode for Header in the spreadsheet gem. It's not being used, so my guess is the developers intend on solving this issue at some point. We have to send the opcode, the length info and the string we want to write out. This was the trickiest part to figure out.

3) We expose an add_header method that simply takes a string and stores it in the header accessor. This means, to set the header, you simply say sheet.add_header("foo header").

To implement the footer, you'd just do the same thing, create a footer accessor, add a method to update it. Then build the writer_footer method with opcode(:footer) and append write_footer at the end of write_from_scratch.

Well, that took us some time to figure out, so enjoy and let me know if you have any questions.

Hello Android - Pindah (with Mirah) Application

Did you install the Android SDK / JDK, etc?  If not, start here - http://developer.android.com/sdk/index.html.
If you're running 64-bit like me, make sure to install the ia32-libs, since the SDK is 32-bit.

This is completely based on the Hello Android tutorial - I didn't really do a whole lot, but the hope is that this will help get some more ruby devs into android development with a simple how-to.

Step 1 - Setup RVM with jruby

Note: RVM is awesome, if you don't use it or don't know about it - read more here.

rvm install jruby
cd /path/to/your/android/pindah/mirah/project/dir/
# using your .rvmrc will trigger `rvm use jruby` when you cd into your project dir.
echo "rvm use jruby" > .rvmrc
# this will make sure your .rvmrc is working, you should then be able
# to use rvm info and see jruby
cd .

Step 2 - Install the mirah and pindah gems

# too easy
gem install mirah pindah

Step 3 - Create your first pindah app

pindah create com.example.android.hello_world
cd hello_world

Step 4 - Create your activity - HelloAndroid.mirah

# from your project dir and inside your pindah app dir
<editor> src/com/example/android/hello_world/HelloWorld.mirah

This is the code I used:

Step 5 - Setup your AndroidManifest.xml file

This is where you define your app, version, name, etc, but more importantly for this example - what activity will handle your main intent.
Mine looks like this:

Step 6 - Install to your device

# make sure a device is recognized  ...
# and make sure adb is in your path (platform-tools in the SDK)
adb devices
rake install

Playing with Mirah

Mirah (formally duby) is pretty freaking cool.   Plans are to scrap java and use mirah for future android development, we'll see.  Here's a rough example of some pretty basic mirah.

To get started, you'll need jruby and the mirah gem:

rvm install jruby
rvm use jruby (or put in your .rvmrc)
gem install mirah

Then create an example:

puts "hello world!!"
500.times do |x|
  puts x
end

Time in ruby:

time ruby test.mirah

...
=> .457s

Compile to Java and time:

mirahc test.mirah
time java Test

....
=> .081s

Less than 1/5 the time and it compiles to Java ... neat

mirahc -j test.mirah

// Generated from test.mirah
public class Test extends java.lang.Object {
  public static void main(java.lang.String[] argv) {
    int __xform_tmp_1 = 0;
    int __xform_tmp_2 = 0;
    int x = 0;
    java.io.PrintStream temp$1 = java.lang.System.out;
    temp$1.println("hello world");
    __xform_tmp_1 = 0;
    __xform_tmp_2 = 500;
    label2:
    while ((__xform_tmp_1 < __xform_tmp_2)) {
      x = __xform_tmp_1;
      label3:
       {
        java.io.PrintStream temp$4 = java.lang.System.out;
        temp$4.println(x);
      }
      __xform_tmp_1 = (__xform_tmp_1 + 1);
    }
  }
}

Using ruby to consolidate a list of numbers by shortening with hyphens

Check it out -

VIN API - ignore checksum validation

It's been mentioned a few times that there should be a way to skip the checksum validation. This means if the check digit calculation generally fails, VIN API will continue to process the VIN to see if there is a "like" VIN match. So here it is:

Vin API - Phase II

We've just finished adding A LOT more details to VIN API's result set. This time we've added things like MPG, MSRP, cargo room/volumn, etc. See the full list below, it is very comprehensive.

If you use ruby (look for a future post with .NET and PHP examples), and want the complete dataset, you would setup your ActiveResource like this:

And then call our API like this:

The only change (for those of you who have already implemented phase I) is to send in a "complete" parameter with value of "true" ... upon doing so, VIN API will send you the complete dataset versus the basic (and default) dataset.

The results would look like this (in XML) and be prepared because it is lengthy:

That's it, just thought I'd share VIN API's Phase II.

2D Vector Graphics in Ruby / Rails

I've been working with Cairo the last day or two to build a sign generator.   I chose Cairo because it seemed like a good fit for building a sign that had to be loss-less in detail and scalable, this rang vector graphics.   I found a few good examples here and there, but they were very few and the documentation was not exactly ruby-friendly.

So I'm going to do a few posts about what I learned and I am going to start with the very basics, since all I could find were completed and elaborate images, way too complicated for a beginner.

Let's start with rotating a square box by 45 degrees.  Very simple.

That's it, pretty simple, right?

Open Flash Chart II and Rails 3

Just a quick note about the Open Flash Chart II plugin for Rails and Rails 3.  Rails 3 did a 180 with regards to ERB tags and security.  Everything is now considered unsafe HTML.  So where we used to be able to do <%= @graph %>, we have to now do <%= @graph.html_safe %>.

Thanks go to kendagriff.

VIN API - VIN Decoder for anyone

UPDATES:
See Phase II details for complete dataset information.
Take a look at the PHP examples and the .NET examples.
And ... while it's been great being able to give this information away freely for about a year now, we have to share some of the cost with our users, so please read about our pricing model.
END UPDATES

VIN API came about through lots of work on a current project of ours - Mr. Quotey.  We are dealing with auto insurance and wanted a way to decode VINs.  The other solutions we found (API-wise) were too expensive for our small, unfunded startup.  So like the way most great things come about, we decided to build our own VIN decoding API.

Using VIN API:

This is explained in detail at VIN API's site, but I will give you a look at what it does here.

If you use Ruby on Rails like I do, then you have the option to use ActiveResource:

Then you can use it like this:

Current Limitations:

Right now each account is limited to 20 VIN requests a month, we are looking to take it slow and prevent abuse.  If you do need more VIN decodings a month, feel free to let us know at Mr. Quotey, we'd be happy to up the max for your account.

Where to next?:

It is too soon to really tell.  We'd like your feedback and to know if this service is useful.  If it gets enough buzz, we would probably pursue it a bit more and drop the monthly limitations.

Ruby PDF Reader Gem Tutorial

I've been doing a lot of work these days dealing with PDFs and for the most part I've been happy with using poppler-utils' pdftohtml. And that is great if you don't care about positioning or formatting and just care about the content. But for those of you who, like me, have run across the need to know text positioning, font size, indentation, coloring, etc., then we will have to use something more.

I had given just about every other option a chance before I finally found the pdf reader gem. But when I found pdf reader, it didn't have much documentation and it wasn't entirely clear how to get started using it and if it would work. Well, I can tell you that it will work and after playing with the examples a lot of it became much clearer. I learned a lot that would probably be useful for a few other people out there, hence this post.
Ok, well to get started, take a look at the github repository for pdf reader. You don't need to spend too much time, but just note a few places like the examples directory and the list of callbacks.

You should probably familiarize yourself with this PDF specification too - found here. It really came in handly when trying to figure out what arguments are being passed around what they represent.

Let's get started -

Step 1:  Install the gem

Yah, this is a pretty easy step, but it is required
sudo gem install pdf-reader

Step 2:  Find a PDF (or PDFs) to use

It would be best to have several PDFs for you to work with since the callbacks could vary depending on the PDF.
NOTE: For these examples, I'm using a really simple PDF, pdf reader could take a while on some PDFs and seem as though it is hanging but it is not, it is just chugging away right around line 283 of this file, reading each byte of your PDF.

Step 3: List the possible callbacks and their args for one of your PDFs

The point of this is to find out what methods we can write for pdf reader to call when it encounters the various parts of our PDF.
The BIG One that you will most likely use is show_text() or some form of it like show_text_with_positioning().
But, for now, THIS all depends on the PDF file you are using, so we need to find out what your PDF uses and go from there.

The easiest way to do this is to follow this example and just substitute "somefile.pdf" with the path to your pdf file.

Run it and you will see a long list of possible callbacks and their arguments. It is likely all squished together, so you can simply change the line of your code that says

to

and get a MUCH better look at everything.

We will start with show_text, so

for show_text and see what you get. For my PDF, I have mostly show_text_with_positioning.

Step 4: Do some lookups

What are the args they are showing me for my callbacks and how do we find out?
You can do this two ways, try your luck at searching the pdf file for "show text" or "show text with positioning" and see what you get. Or you can lookup the token used to represent show_text or show_text_with_positioning.
The first way is pretty obvious, so on to the second - look in the list of callbacks I had your familiarize yourself with earlier, starting on line 172. Looking through we can find show_text and show_text_with_positioning, having Tj and TJ as their operators. Alright, now we have something to look up - "TJ". Well, I found it on page 251 of the PDF Specification from earlier. Some of descriptions for the operators will require rereading but you will get the hang of it.

Step 5: Use what we found

Now that we know how the show_text_with_positioning works and what args it brings in, we can write our code.
We need an instance of a receiver to pass to the PDF Reader. This is just a class that has methods likes show_text() of show_text_with_positioning(). Our receiver could look something like this:

Now we just need to create our receiver instance an pass our PDF file to pdf reader:

Don't forget to require the pdf reader at the top of your script like this:

Step 6: Check out the results

If we run our script, we will see all the text that uses Tj or TJ print out.

This is just the beginning and you can pick and choose any of the callbacks from that list (list of operators) and implement just about anything.

At the beginning of this post, I mentioned that I was concerned about positioning. This means I had to get very familiar with the text matrix operator (Tm), found on page 250 of the specification. It takes six arguments (a-f) all representing one thing or another and it is not very well documented. From what I can gather, the first four (a through d) are for things like scale and rotation, the last two e and f are for position on the page, where e is along the x axis and f along the y axis.

There is another text positioning operator that I saw quite often and that is move_text_position (Td operator, page 249 of the specification) that actually provides the x and y (unscaled) text space units coordinates. So if y is -1, that just means go to the next line and if y is 0, stay on the same line, -2, move down two lines, 2, move up two lines, etc. x is for indentation or horizontal spacing and represents the number of characters (spaces) to offset the text position by.

I hope this helps and a huge thanks goes to James Healy for his grand work on pdf reader.