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RubyMotion – PullToRefresh

To add Sam Vermette’s SVPullToRefresh to your RubyMotion project:

  1. Add the SVPullToRefresh pod
  2. Add the Quartz Framework

Then – in your controller

Posted in Ruby, RubyMotion.

Using NUI with RubyMotion

NUI is an open-source library that allows you to style your iOS applications using CSS-like files and syntax. In my opinion, NUI carries few benefits over its commercial, KickStart backed, competitor Pixate. First; NUI allows you to style your application on the fly while it’s running in the simulator. And Second; NUI styled-elements are not masked/wrapped in their special classes (like those PX* classes with pixate), rather, they remain as their original iOS declarations. The second point makes debugging the simulated application and tracking ons-creen objects (using cmd-hover) much easier.


In your RubyMotion application’s Rakefile:

Then run rake clean & rake


Create a theme.nss file (which will include your application’s stylesheet). Then in your app_delegate.rb

Run rake and check your application in the simulator. Now, any changes to the theme.nss file will be reflected right away to the running application in the simulator.

Happy styling

Posted in iOS, Ruby, RubyMotion.

Consultancy Masterclass

Last weekend, I sat through the two-day Consultancy Masterlcass by Brennan Dunn & Obie Fernandez. Both Brennan and Obie have extensive experience building their own successful consultancy firms.

The class was insightful and full of those ‘from the trenches’ experiences. What was of significant value is the knowledge transparently shared by students and alumni. All of whom are of similar mindsets and are taking their steps in establishing their own names in the consultancy world. I look forward to being part of a great community.

Posted in Professional, Ruby.

Thoughts on building vs growing

Many times I’ve heard professionals talk and plan out building software applications. Great ideas they’d like seen implemented, and how it could make things better. Though might not seem obvious – software applications, at least the good, are never built.

Applications are grown.[1]

There’s quite the range of differences between building an application and growing one, but I’ll focus here on few main ones.

Building something is associated with a resulting rigid structure and components. It takes effort to put together, but once build – it’s static. All what’s left is usage, admiration & maintenance.

On the other hand, growing something is an organic process. It rarely stops. It requires a continuous labour of love. You can reap benefits but as you do, you always have to give back, care and nurture.

Growing is more appropriate to the act of developing software. Applications doesn’t (or shouldn’t) reach a static rigid state, they always benefit from continuous assessment, reevaluation and changes. They adjust to surroundings. They evolve, transform and get bigger (but not necessarily more complex).
So – next time you’re discussing new applications – try to see how close the word ‘growing’ is to everyone.

[1] I wish I could remember where first I heard that or who said it.

Posted in General, Professional.

Rails and inner query choices

Consider that we have two models; Well and SurveyPoint . A Well represent an oil/gas/water well, each with multiple SurveyPoints. A SurveyPoint represent the well’s coordinate at a certain depth.

Say, we’d like to implement a filtration mechanism that allows us to query the wells – and for those set of wells we’d like to conditionally present the set of survey_points for those set of filtered wells.

A method ‘’ would returns the set of wells we’re interested in ( @wells )

Using the power of AREL chaining, we could then conditionally extract the SurveyPoints using the following:

This roughly translates into the query:

The challenge here is that if both results is large, depending on the cardinality – the database engine might not be able to make use of defined indexes and the outer query might not be optimizable.

Instead – if we use pluck instead of select:

Rails would fire two queries instead of an inner one. Pluck would first extract the list of ids (val_1, val_2, …) in an array before passing it to the main query. This roughly translates into:

No inner query is used in that case and the main one is easy to optimize.

Posted in Ruby.

JRuby – can’t convert Hash into String

I’ve recently upgraded a JRuby/Rails application from JRuby 1.6.3 (1.8 compatibility mode) to 1.6.8 (1.9 mode). Everything was working out fine except for actions relying on internal CSV library (FasterCSV in 1.8 mode). The error can't convert Hash into String was thrown as CSV tries to generate the csv string.

This had the hallmarks that the application was still under the 1.8 mode (after a deploy to tomcat). The following XML entry in web.xml was essential to enforce the 1.9 mode:

Posted in Java, Ruby.

newrelic – undefined method `-‘ for nil:NilClass

Using JRuby with trinidad (developer mode) – I was intermittently getting this error. Apparently thrown as estimated_time for the transaction was returning nil. I was also having all sorts of other issues (undefined method `metric_name’ for nil:NilClass) with all newrelics action summaries.

To resolve (following suggestions on the trinidad google group):

According to Nick Sieger’s gist – “NewRelic isn’t detecting Trinidad at the moment” – Although I could see trinidad’s detection mechanism implemented in newrelic’s most recent (

I’ve tried it with more recent versions of newrelic – but it seems 3.3.0 is the most stable.

JRuby 1.6.8 (1.9 mode)

trinidad 1.4.4

newrelic_rpm 3.3.0


Getting another error of undefined method `first' for true:TrueClass. The error is apparently thrown if the “EXPLAIN” query has failed against the DB engine. Although – I got the transaction_tracing disabled with explain_enabled set to false – yet this release still attempts to fire the “EXPLAIN” against the DB.

Since I’m using the oracle_enhanced_adapter, the current newrelic “EXPLAIN” query wouldn’t work – hence an error is thrown. However, the error consumption by newrelic returns true rather than nil.

Changing handle_exception_in_explain to return nil instead of the true fixes it.

Posted in Java, Ruby, Web.

JRuby/Rails Streaming in development environment (and beyond)

Rails streaming is a great feature that allows you to optimize on server resources when dealing with large generated content. However – it might be a bit tricky to validate and test in local development.

First off – a local server that supports streaming is required. The only one I could find was trinidad which is moving to the likely defacto for JRuby/Rails projects. Trinidad uses tomcat-core as it’s servlet container and server.

Then make sure you grab the latest jruby-rack resolving most recent issues (1.1.10 at the time of writing).

This StackOverflow answer, along with this guide offer a comprehensive support as to what options work with Rails version as well as some gotchas (newrelic, caching, haml, …).

For Rails 3.2.x – It boils down to assigning an object that responds to an each method call to the response_body of a controller’s action. However – this doesn’t allow you to set a :stream =>true where it explicitly tells Rails to stream the respons. To resolve that I opted to use a render call, with a passed option hash as follows:

This works with the following releases:
JRuby 1.6.8
Rails 3.2.8
jruby-rack 1.1.10
trinidad 1.4.4

Posted in Ruby.

JQuery Autocomplete updating a document element (not the dropdown)

I came across the requirement of updating a page element from the result of an Autocomplete. The server results were to be placed in a select element as set of option items.

I had to overwrite some JQuery UI Autocomplete private methods as apparently there was no easy way of generating HTML and embedding it in the right spot on the page:

The JSON server response:

JQuery 1.8.16
Rails 3.1

Posted in Ruby, Web.

JRuby and Polyglot

JRuby 1.5.6 (I know. Old)
Rails 3.0.1
Polyglot 0.3.3

UPDATE: see easier fix below

Getting the following error when bundling:

JRuby YAML parser is erring with this version of Polyglot (don’t you love JRuby!!).

‘gem dependency -R polyglot’ will get you the reverse dependencies on the library. In this case it’s ‘treetop’

Had to edit the ‘gemspec’ files and restrict the version of polyglot to ‘< 0.3.3' Example - From s.add_runtime_dependency(%q , [“>= 0″])
s.add_runtime_dependency(%q , [“>= 0″, “< 0.3.3"]) Yak shaving!!! UPDATE: EASIER FIX: just use gem ‘polyglot’, ‘0.3.2’ in your Gemfile, it might just do the trick.

Posted in Ruby.