Flowdock

Notes posted by Oleg

RSS feed
July 15, 2010
0 thanks

Doesn't output into STDOUT

Oddly enough it runs a rake task without any sort of output. To get around it you can simple substitute it with:

puts run('rake your_task')

Unless somebody has a better idea?

July 14, 2010
2 thanks
July 14, 2010
0 thanks

If you need to pass a value

In the above example ‘value’ happens to be either true or false depending if the option was passed in or not. If you wish to capture an actual value you’ll want something like this:

def add_options!(opt)
  opt.on('-option=value') { |value| options[:option] = value }
end
June 23, 2010
1 thank

Doesn't handle nested hashes

If you pass something like this:

http.set_form_data({:a => {:b => :c}})

it will completely mangle the value. So don’t use it.

June 18, 2010
0 thanks

Careful when updating foreign key directly

Seems when you change key directly it doesn’t update association automatically.

>> chicken = Chicken.first
>> chicken.head
=> old_head
>> chicken.head_id = new_head.id
>> chicken.head
=> old_head

Easy (stupid?) way to fix it:

class Chicken
  def head_id=(value)
    self.head = Head.find_by_id(value)
  end
end
November 5, 2009
6 thanks

define_method with parameters

Just to be clear, you can do this:

define_method(:my_method) do |foo, bar| # or even |*args|
  # do something
end

This means same as:

def my_method(foo, bar)
  # do something
end

If you want to define method with parameters that have default values, you need to get a bit more creative and do something like this:

define_method(:my_method) do |foo, bar|
  bar ||= {}
  # do something
end
June 12, 2009
3 thanks

cattr_accessor_with_default

Class attribute assessors are neat if you want to set up modifiable constant-like varibles. This is how you’d normally set it up:

module MyPlugin
  class Conf
    @@awesome_level = 'huge'
    cattr_accessor :awesome_level
  end
end

Then you can call and modify it like this:

>> MyPlugin::Conf.awesome_level
=> 'huge'
>> MyPlugin::Conf.awesome_level = 'massive'
>> MyPlugin::Conf.awesome_level
=> 'massive'

If you have a pile of those accessors I’d do something like this (there might be a better way, but it works):

module MyPlugin
  class Conf
    def self.cattr_accessor_with_default(name, value = nil)
      cattr_accessor name
      self.send("#{name}=", value) if value
    end

    cattr_accessor_with_default :awesome_level, 'huge'
    cattr_accessor_with_default :speed_level, 'insane'
    cattr_accessor_with_default :indifferent_level
    cattr_accessor_with_default :craziness_level, 'nuts'
  end
end

This way you declare accessor and it’s optional default value on the same line

June 10, 2009
2 thanks

[:a, :b, :c].try([1]) ? The answer is No.

Correct way is this:

[:a, :b, :c].try(:at, 1)
April 30, 2009
1 thank

Find random record

It’s as simple as:

Things.first(:order => 'RAND()')

Of course depending on your database it could be ‘RANDOM()’ or something similar.

April 23, 2009
5 thanks

Handy shorthand for array manipulation

You may write something like this:

>> ['a', 'b', 'c'].collect{|letter| letter.capitalize}
=> ["A", "B", "C"]

But it looks so much nicer this way:

>> ['a', 'b', 'c'].collect(&:capitalize)
=> ["A", "B", "C"]
April 6, 2009
5 thanks

HTML entities in options

Unfortunately everything is escaped with ERB::Util#html_escape. Your only option is either manually construct options or compeletely overwrite this method.

April 6, 2009
6 thanks

Array clustering

Sometimes you don’t want to mangle sequence of an array and just want to group adjacent values. Here’s a nice method to do so (drop it in your initializers directory or something):

module Enumerable
  # clumps adjacent elements together
  # >> [2,2,2,3,3,4,2,2,1].cluster{|x| x}
  # => [[2, 2, 2], [3, 3], [4], [2, 2], [1]]
  def cluster
    cluster = []
    each do |element|
      if cluster.last && yield(cluster.last.last) == yield(element)
        cluster.last << element
      else
        cluster << [element]
      end
    end
    cluster
  end
end

Similarly you can do the clustering on more complex items. For instance you want to cluster Documents on creation date and their type:

Document.all.cluster{|document| [document.created_on, document.type]}
April 6, 2009
3 thanks

Take care when writing regex

When you want to validate a field for a continuous string you’d probably write something like this (if it’s really early in the morning and you didn’t have your coffee yet):

validates_format_of :something => /\w/

At the first sight it looks like it’s working because something = “blahblahblah” is valid. However, so is this: something = “blah meh 55”. It’s just that your regex matched a substring of the value and not the whole thing. The proper regex you’re looking for is actually:

validates_format_of :something => /^\w$/
March 5, 2009
7 thanks

String#match will match single token only

>> s = “{{person}} ate {{thing}}”

> “{{person}} ate {{thing}}”

>> r = /{{(.*?)}}/

> {{}}

>> s.match®.captures

> [“person”]

Using String#scan pulls out all tokens you were searching for:

>> s.scan®.flatten

> [“person”, “thing”]

February 9, 2009
5 thanks