# Class arguments (newbe question)

**URL:** <https://rubytalk.org/t/class-arguments-newbe-question/56497>\
**Category:** ruby-talk\
**Created:** [5 December 2009 09:17 UTC](https://rubytalk.org/t/class-arguments-newbe-question/56497 "2009-12-05T09:17:23Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![Panagiotis\_Atmatzidi](https://avatars.discourse-cdn.com/v4/letter/p/a88e4f/32.png) [@Panagiotis\_Atmatzidi](https://rubytalk.org/u/Panagiotis_Atmatzidi)\
**Post date:** [5 December 2009 09:17 UTC](https://rubytalk.org/t/class-arguments-newbe-question/56497/1 "2009-12-05T09:17:23Z")

</div>

Hello to the list!

I have the following code which prints the ip's from fail2ban.log and puts then in an array:

- --------------------------  
class ReadIPs  
&nbsp;&nbsp;attr\_accessor :ip  
&nbsp;&nbsp;def initialize(ip)  
&nbsp;&nbsp;&nbsp;&nbsp;@ip = ip  
&nbsp;&nbsp;end  
&nbsp;&nbsp;  
&nbsp;&nbsp;def ip(filename)  
&nbsp;&nbsp;&nbsp;&nbsp;ips = []  
&nbsp;&nbsp;&nbsp;&nbsp;File.read(filename).lines.to\_a.each do |place|  
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;sf = 0  
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;while sfn = place.index(/(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)/,sf)  
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;sf = sfn + 3  
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;ips \<\< $&  
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;end  
&nbsp;&nbsp;&nbsp;&nbsp;end  
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return ips  
&nbsp;&nbsp;end  
end

# print methods

a = ReadIPs.new("/Users/atma/Projects/ZoneReport/log/fail2ban.log")  
puts a.ip("/Users/atma/Projects/ZoneReport/log/fail2ban.log")

- ---------------------------------

What I don't understand is why do I need to give the argument to the new instance of ReadIPs.new class. In my view the code should look like:

a = ReadIPs.new  
puts a.ip("/Users/atma/Projects/ZoneReport/log/fail2ban.log")  
- ----------------------------------

But this returns an error and does not run. Can someone please drop a few light here please 🙂

best regards & thanks in advance

Panagiotis (atmosx) Atmatzidis

email: [atma@convalesco.org](mailto:atma@convalesco.org)  
URL: [http://www.convalesco.org](http://www.convalesco.org)  
GnuPG ID: 0xFC4E8BB4  
gpg --keyserver x-hkp://pgp.mit.edu --recv-keys 0xFC4E8BB4  
- --  
The wise man said: "Never argue with an idiot. They bring you down to their level and beat you with experience."

---

<div class="post-metadata">

**Author:** ![Jesus\_Gabriel\_y\_Gala](https://avatars.discourse-cdn.com/v4/letter/j/96bed5/32.png) [@Jesus\_Gabriel\_y\_Gala](https://rubytalk.org/u/Jesus_Gabriel_y_Gala)\
**Post date:** [5 December 2009 09:55 UTC](https://rubytalk.org/t/class-arguments-newbe-question/56497/2 "2009-12-05T09:55:55Z")

</div>

> -----BEGIN PGP SIGNED MESSAGE-----  
> Hash: SHA1
> 
> Hello to the list!
> 
> I have the following code which prints the ip's from fail2ban.log and puts then in an array:
> 
> - --------------------------  
> class ReadIPs  
> attr\_accessor :ip  
> def initialize(ip)  
> @ip = ip  
> end

When you define an initialize method that receives an argument, you  
must pass an argument when you create an instance with new.

> def ip(filename)  
> ips =   
> File.read(filename).lines.to\_a.each do |place|  
> sf = 0  
> while sfn = place.index(/(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)/,sf)  
> sf = sfn + 3  
> ips \<\< $&  
> end  
> end  
> return ips  
> end  
> end
> 
> # print methods
> 
> a = ReadIPs.new("/Users/atma/Projects/ZoneReport/log/fail2ban.log")  
> puts a.ip("/Users/atma/Projects/ZoneReport/log/fail2ban.log")
> 
> - ---------------------------------
> 
> What I don't understand is why do I need to give the argument to the new instance of ReadIPs.new class. In my view the code should look like:
> 
> a = ReadIPs.new  
> puts a.ip("/Users/atma/Projects/ZoneReport/log/fail2ban.log")

Then you can remove the initialize method from the ReadIPs class. In  
fact, if that's the only thing you are going to do, you don't even  
need a to be an instance. You can have a class method instead, since  
you are not maintaining state:

class ReadIPs  
&nbsp;&nbsp;def self.ip(filename)  
&nbsp;&nbsp;...  
&nbsp;&nbsp;end  
end

and call it like

ReadIPs.ip("/Users/atma/Projects/ZoneReport/log/fail2ban.log")

Another possibility is to maintain the calculated array of matched IPs  
in an instance, so what I would do in that case is:

class ReadIPs  
&nbsp;&nbsp;attr\_reader :ips

&nbsp;&nbsp;def initialize file\_name  
&nbsp;&nbsp;&nbsp;&nbsp;@ips = perform the algorithm to match the ips.  
&nbsp;&nbsp;end  
end

and then you can do:

a = ReadIPs.new("/Users/atma/Projects/ZoneReport/log/fail2ban.log")

which will calculate the ips and store them in the instance variable.  
Then you can call:

a.ips

which will return the stored array.

Hope this helps,

Jesus.

> **···**
>
> On Sat, Dec 5, 2009 at 10:17 AM, Panagiotis Atmatzidis \<atma@convalesco.org\> wrote:

---

<div class="post-metadata">

**Author:** ![Panagiotis\_Atmatzidi](https://avatars.discourse-cdn.com/v4/letter/p/a88e4f/32.png) [@Panagiotis\_Atmatzidi](https://rubytalk.org/u/Panagiotis_Atmatzidi)\
**Post date:** [5 December 2009 10:12 UTC](https://rubytalk.org/t/class-arguments-newbe-question/56497/3 "2009-12-05T10:12:01Z")

</div>

It helped a lot! Thank you for the prompt & detailed answer

Panagiotis (atmosx) Atmatzidis

email: atma@convalesco.org  
URL: [http://www.convalesco.org](http://www.convalesco.org)  
GnuPG ID: 0xFC4E8BB4  
gpg --keyserver x-hkp://pgp.mit.edu --recv-keys 0xFC4E8BB4

> **···**
>
> On 05 Δεκ 2009, at 11:55 π.μ., Jesús Gabriel y Galán wrote:
> 
> > On Sat, Dec 5, 2009 at 10:17 AM, Panagiotis Atmatzidis \> \<atma@convalesco.org\> wrote:
> > 
> > > -----BEGIN PGP SIGNED MESSAGE-----  
> > > Hash: SHA1
> > > 
> > > Hello to the list!
> > > 
> > > I have the following code which prints the ip's from fail2ban.log and puts then in an array:
> > > 
> > > - --------------------------  
> > > class ReadIPs  
> > > attr\_accessor :ip  
> > > def initialize(ip)  
> > > &nbsp;&nbsp;&nbsp;@ip = ip  
> > > end
> > 
> > When you define an initialize method that receives an argument, you  
> > must pass an argument when you create an instance with new.
> > 
> > > def ip(filename)  
> > > &nbsp;&nbsp;&nbsp;ips =   
> > > &nbsp;&nbsp;&nbsp;File.read(filename).lines.to\_a.each do |place|  
> > > &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;sf = 0  
> > > &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;while sfn = place.index(/(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)/,sf)  
> > > &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;sf = sfn + 3  
> > > &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;ips \<\< $&  
> > > &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;end  
> > > &nbsp;&nbsp;&nbsp;end  
> > > &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return ips  
> > > end  
> > > end
> > > 
> > > # print methods
> > > 
> > > a = ReadIPs.new("/Users/atma/Projects/ZoneReport/log/fail2ban.log")  
> > > puts a.ip("/Users/atma/Projects/ZoneReport/log/fail2ban.log")
> > > 
> > > - ---------------------------------
> > > 
> > > What I don't understand is why do I need to give the argument to the new instance of ReadIPs.new class. In my view the code should look like:
> > > 
> > > a = ReadIPs.new  
> > > puts a.ip("/Users/atma/Projects/ZoneReport/log/fail2ban.log")
> > 
> > Then you can remove the initialize method from the ReadIPs class. In  
> > fact, if that's the only thing you are going to do, you don't even  
> > need a to be an instance. You can have a class method instead, since  
> > you are not maintaining state:
> > 
> > class ReadIPs  
> > def self.ip(filename)  
> > ...  
> > end  
> > end
> > 
> > and call it like
> > 
> > ReadIPs.ip("/Users/atma/Projects/ZoneReport/log/fail2ban.log")
> > 
> > Another possibility is to maintain the calculated array of matched IPs  
> > in an instance, so what I would do in that case is:
> > 
> > class ReadIPs  
> > attr\_reader :ips
> > 
> > def initialize file\_name  
> > &nbsp;&nbsp;&nbsp;@ips = perform the algorithm to match the ips.  
> > end  
> > end
> > 
> > and then you can do:
> > 
> > a = ReadIPs.new("/Users/atma/Projects/ZoneReport/log/fail2ban.log")
> > 
> > which will calculate the ips and store them in the instance variable.  
> > Then you can call:
> > 
> > a.ips
> > 
> > which will return the stored array.
> > 
> > Hope this helps,
> 
> --  
> The wise man said: "Never argue with an idiot. They bring you down to their level and beat you with experience."