blank? Is All You Need

if data.nil? || data.blank?
  inform_user
end

I've seen the above code often enough lately that I thought a brief post was in order to inform/remind folks that blank? is all you need. Here's a script/console session proving just that.

$ script/console
Loading development environment (Rails 2.3.5)
>> data = nil
=> nil
>> data.nil?
=> true
>> data.blank?
=> true

Thus, we can eliminate the first half of the conditional expression.

if data.blank?
  inform_user
end

Now, if you find you want to check !blank? but you prefer to express your conditional checks positively instead of negatively, you can use present?.

if !data.blank?
  show_it
end

becomes

if data.present?
  show_it
end

Using blank? and present? enables clearer and more concise conditionals, a benefit not only now but every time someone reads the code.

Using script/console with jruby-complete

On my current project, we're trying jruby-complete 1.4.0 in development. I'm new to JRuby. The one thing I haven't liked so far was that I couldn't figure out how to use script/console. What I expected to work didn't:

$ java -Xmx500m -Xss1024k -jar path/to/jruby-complete-1.4.0.jar -S script/console
Loading development environment (Rails 2.3.5)
Error opening script file: /Users/cdemyanovich/work/my_project/file:/path/to/jruby-complete-1.4.0.jar!/META-INF/jruby.home/bin/jirb (No such file or directory)

Searching Google by several different combinations of terms from my error message proved fruitless. I joined the #jrubyonrails IRC channel on freenode, greeted everyone, asked my question and received an answer from nicksieger in minutes.

$ java -Xmx500m -Xss1024k -jar path/to/jruby-complete-1.4.0.jar -S irb
irb(main):001:0> require 'config/environment'
JRuby limited openssl loaded. gem install jruby-openssl for full support.
http://jruby.kenai.com/pages/JRuby_Builtin_OpenSSL
=> true
irb(main):002:0> User.count
=> 1
irb(main):003:0> 

I'm happy to have this oft-used tool working again. If you have any other problems with JRuby, you'll find friendly experts ready, willing and able to help in the #jruby and #jrubyonrails channels on freenode.

Viewing local websites in the Android emulator

I've been working on a mobile UI for a website. I'm using iUI to make the site work well in Mobile Safari on the iPhone and iPod touch. iUI should work well for the browser on Android, too, since it's also WebKit-based. With that in mind, I downloaded the Android SDK and Eclipse, created an Android Virtual Device (AVD), and launched the emulator.

Unlike the iPhone Simulator (included with the iPhone SDK), the Android emulator just wouldn't load my site by the name I was using locally. Strangely, 127.0.0.1 wouldn't work either, not even with a port number. Frustratingly, I entered my local IP address and a port number in the browser, and I was able to view my site on the emulator.

This morning, some searching revealed that many people hit this same wall. What I found is that localhost and 127.0.0.1 in the Android emulator refer to its own loopback interfaces. To browse to websites on your machine, use 10.0.2.2 instead. Here's the official word from the Android Developer's Guide.