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Disabeling sessions in Rails

Friday, November 23rd, 2007

The simplest way to disable sessions in Rails is to use session :off (see ActionController::SessionManagement::ClassMethods).

session :off

To disable session suport only for a specific controller add session :off to that controller

class MyController < ApplicationController
    session :off
end

Written like that, sessions are disabled for all actions on this controller.

Like filters, you can specify :only and :except clauses to restrict subset. The following code will disable session for first_action and third_action, but not for second_action.

class MyController < ApplicationController
  session :off, :only %w(first_action third_action)

  def first_action
  end

  def second_action
  end

  def third_action
  end
end

(more…)

Posted in Rails | 1 Comment »

Determining the number of days in a month

Wednesday, August 22nd, 2007

Here is a simple method that returns number of days for wanted month and year. If year is ommited current year is selected.

def month_days(month, year=Date.today.year)
  mdays = [nil, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
  mdays[2] = 29 if Date.leap?(year)mdays[month]
end

Simple examples:

month_days(1)       => 31
month_days(2, 2007) => 28
month_days(2, 2008) => 29

Now, let’s assume we have a date from a database, and we want to find number of days in a month from that date.

month_days(date.month, date.year)

But with two more lines of code

(more…)

Posted in Rails, Ruby | No Comments »

Ruby Inject

Friday, August 3rd, 2007

You probably frequently have to iterate through a list and accumulate a result that changes as you iterate. Let’s take the following array: 

nums = [1, 3, 5, 7]

If you want to find a sum of all the items in the array, you could write something like this:

sum = 0
nums.each { |n| sum += n }

This works fine, but it doesn’t look much elegant. Luckly, for us that wants to be elegant there is a inject method.
(See: Enumerable::inject)

sum = nums.inject(0) { |x,n| x+n }

This code does the same thing, but also looks cool. Inject acomplish this by using accumulator or accumulated value (x). At each step accumulated value is set to the value returned by the block. Here, we set accumulator initial value to 0, and at each step current value from array (n) is added to accumulated value.

If initial value is omitted, the first item is used as the accumulator initial value and is then omitted from iteration.

sum = nums.inject { |x,n| x+n }

Is same as

sum = nums[0]
nums[1..-1].each { |n| sum += n }

Another example.
We have array with five names:

names = ["michael", "ron", "scottie", "dennis", "toni"]

The following code:

string = names.inject("") { |x,n| x << "#{n} " }

Will output:

=> "michael ron scottie dennis toni "

You can get the same output with:

string = ""
names.each { |n| string << "#{n} "}

Now, let’s say you won’t to separate them with comma, and capitalize those that have more then four characters.
You can do it like this:

string = ""
names.each do |n|
  name = n.length > 4 ? n.capitalize : n
  n == names.last ? string << name : string << "#{name}, "
end

Or like this:

string = names.inject("") do |x,n|
  name = n.length > 4 ? n.capitalize : n
  n == names.last ? x << name : x << "#{name}, "
end

In both ways we get the same result:

=> "Michael, ron, Scottie, Dennis, toni"

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Posted in Ruby | 8 Comments »

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