Converting nil

Check C,C++,Java, JavaScript or any other langugage which treats “nil” as something different–probably a meaning equivalent to “a person having 5 hands”. But in Ruby you may use

nil.to_s —>> “0″

nil.to_i —->> 0

Is this really breaking the original stream of programming languages?

Visibility of a method

By default methods within a class in Ruby is PUBLIC. But as we know, ruby supports meta programming and hence a new/updated code can be generated on fly during the runtime.
here is a way to make the public class methods to private.

class Myclass
  def mymethod
    puts "I am public and wishing to be private!"
  end
  private :mymethod
  # OR also can be written as
  # private_class_method :mymethod
end

obj = Myclass.new
obj.mymethod
# private method `mymethod' called for # (NoMethodError)

Similary public :mymethod or public_class_method :mymethod

Ruby security vulnerabilities

Multiple arbitrary code execution vulnerabilities in Ruby have been revealed by the Apple Product Security team which could lead to Denial of Service attacks. A total of five vulnerabilities have been reported, with versions impacted being:

1.8.4 and all prior versions
1.8.5-p230 and all prior versions
1.8.6-p229 and all prior versions
1.8.7-p21 and all prior versions
1.9.0-1 and all prior versions

Upgrading to either 1.8.5-p231, 1.8.6-p230, 1.8.7-p22 or 1.9.0-2 is recommended.

Details could be found at

http://weblog.rubyonrails.org/2008/6/21/multiple-ruby-security-vulnerabilities

http://www.ruby-lang.org/en/news/2008/06/20/arbitrary-code-execution-vulnerabilities

Generate Unique ID

Here is a very simple way to generate a unique id.
[Background support : Abhishek S.]

def generate_unique_id( len )
    chars_pattern = ("a".."z").to_a + ("A".."Z").to_a + ("0".."9").to_a
    unique_id = ""
    1.upto(len) {
			|i| unique_id << chars_pattern[rand(chars_pattern.size-1)]  }
    return unique_id
end
#generates a key of length 10
mykey = generate_unique_id(10)
print mykey # gives a result like "qeKX0myIQh"

Sorting an Array of hashes

We get a situation where we fetch some set of records from db as an array of hashes, and later we need to sort this array based on some field of DB.

Here is a very hand code to do so.

array_objs =[ {:title => "row1_title" ,:name => "Mumbai"},
              {:title => "row2_title" ,:name => "Delhi"},
              {:title => "row3_title" ,:name => "Bangalore"}  ]

array_objs .sort_by  {|array_objs|   array_objs [:name] }.each do |res|
  puts "#{res[:name] }"
end

O/P:
Bangalore
Delhi
Mumbai

Exception Handling in Ruby

>begin expression executes its body and returns the value of the last evaluated expression.
>Any error in begin part will be caught by rescue depending upon parameters
>ensure is the one which must be exectued irrespective of exception occured or not
>An error message caught by an exception can be accessed using $!

For Java Programmers [ begin => try ; rescue => catch; ensure => finally]

begin
 p "I am doing well"
 p "so well .. and well"
 a = 8/0
rescue
 p "Something went wrong => " + $!
ensure
 p "Oh Somehow I could finish my work"
end

O/P:

“I am doing well”
“so well .. and well”
“Something went wrong => divided by 0″
“Oh Somehow I could finish my work”

a = 8
b = 0
begin
 p "I am doing well"
 p "so well .. and well"
 if a==18
    p "I am happy with a as 8"
 elsif b == 0
    p "Lets say I dont want this"
    raise Exception
 else
    raise
 end

rescue
    p "Exception 1 caught here " + $!
rescue Exception
    p "Exception 2 caught here " +$!
ensure
 p "Oh Somehow I could finish my work"
end

O/P for [[ a = 8 and b = 0 ]]
“I am doing well”
“so well .. and well”
“Lets say I dont want this”
“Exception 2 caught here Exception”
“Oh Somehow I could finish my work”

O/P for [[ a = 8 and b = 1 ]]
“I am doing well”
“so well .. and well”
“Exception 1 caught here “
“Oh Somehow I could finish my work”