# Question on setting up a class and searching on objects **URL:** \ **Category:** Ruby\ **Created:** [August 15, 2006, 2:16pm UTC](https://www.ruby-forum.com/t/question-on-setting-up-a-class-and-searching-on-objects/102382 "2006-08-15T14:16:39Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![zanoni](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/z/e99b99/32.png) [@zanoni](https://www.ruby-forum.com/u/zanoni)\ **Post date:** [August 15, 2006, 2:16pm UTC](https://www.ruby-forum.com/t/question-on-setting-up-a-class-and-searching-on-objects/102382/1 "2006-08-15T14:16:39Z")
I’m working from Ruby for Rails book but want to try and just replicate some of the examples in Ruby alone. One method in particular is called whole\_name and would give the user the ability to search a list by first\_name, middle\_name, or last\_name. So I went ahead and set up my class and objects, but have a few questions (below code) class Composer def listcomp (first\_name, middle\_name, last\_name) f = first\_name m = middle\_name l = last\_name end def whole\_name first\_name + " " + (if middle\_name then middle\_name + " " else “” end) + last\_name end end comp1 = Composer.new comp2 = Composer.new comp3 = Composer.new comp4 = Composer.new comp5 = Composer.new comp1.listcomp(“ludwig”,“van”,“bethoven”) comp2.listcomp(“wolfgang”,“amadeus”,“mozart”) comp3.listcomp(“franz”, “joseph”, “hayden”) comp4.listcomp(“George”, “frederic”, “Handel”) comp5.listcomp(“Johann”, “sebastian”, “bach”) Question - I’m having a problem calling to the class method whole\_name. The method is defined without any arguments so how could it be called ? Question - Did I set up the class correctly , defining the new object outside of the class definition ? And would it be better to create an array (multidimensional) for the composers instead of initializing each one seperately ? (If this question makes sense) Apologies if this question is sort of lame. TIA Stuart ---
**Author:** ![zanoni](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/z/e99b99/32.png) [@zanoni](https://www.ruby-forum.com/u/zanoni)\ **Post date:** [August 15, 2006, 2:16pm UTC](https://www.ruby-forum.com/t/question-on-setting-up-a-class-and-searching-on-objects/102382/2 "2006-08-15T14:16:44Z")
On Aug 11, 2006, at 7:47 AM, Dark A. wrote: > I’m working from Ruby for Rails book but want to try and just > replicate some of the examples in Ruby alone. > One method in particular is called whole\_name and would give the user > the ability to search a list by first\_name, middle\_name, or last\_name. If you want to make a method to search the the individual composers, you will need to get them into some data structure (like an Array) where you can scan through them. > class Composer > > def listcomp (first\_name, middle\_name, last\_name) > f = first\_name > m = middle\_name > l = last\_name > end What are you intending this method to do? Currently, it doesn’t do anything meaningful: 1. first\_name, middle\_name, and last\_name are accepted as arguments 2. Each of those is assigned to another local variable 3. All six local variables are discarded as the method exits > def whole\_name > first\_name + " " + > (if middle\_name then middle\_name + " " else “” end) + > last\_name > end > end This method doesn’t work because it uses local variables that don’t exist in this method. I believe this is your hang-up. Inside a class, you keep data around by putting it into instance variables (those start with an @ symbol). All methods of the class can access the instance variables for the current object. See if this helps explain things: > > class Name > > def initialize(first, last, middle = nil) > > # assign these local variables to instance variables… > > ?\> @first = first > > > ``` > > @last = last > > @middle = middle > > > > ``` > > > > end ?\> # create methods to read those instance variables… ?\> attr\_reader :first, :last, :middle > > ?\> def full > > ``` > > [@first, @middle, @last].join(" ").squeeze(" ") > > > > ``` > > > > end > > end > > =\> nil > > > james = Name.new(“James”, “Gray”, “Edward”) > > =\> #\ > > > james.last > > =\> “Gray” > > > james.full > > =\> “James Edward G.” > > > dana = Name.new(“Dana”, “Gray”) > > =\> #\ > > > dana.middle > > =\> nil > > > dana.full > > =\> “Dana Gray” > comp5.listcomp(“Johann”, “sebastian”, “bach”) > Here’s another idea: > > composers = [%w[ludwig van beethoven], > > ?\> %w[wolfgan amadeus mozart], > > ?\> %w[franz joseph hayden], > > ?\> %w[george frederic handel], > > ?\> %w[johann sebastian bach] ].map do |f, m, l| > > ?\> Name.new(f, m, l) > > > end > > =\> [#\ > @middle=“beethoven”\>, #\ > @first=“wolfgan”, @middle=“mozart”\>, #\ > @first=“franz”, @middle=“hayden”\>, #\ > @first=“george”, @middle=“handel”\>, #\ > @last=“sebastian”, @first=“johann”, @middle=“bach”\>] > Question - I’m having a problem calling to the class method > whole\_name. The method is defined without any arguments so how could > it be called ? whole\_name() is not a class method, it is an instance method. You know this because it is called on instances of the class, not the class itself (new() is a class method). I hope my examples above cleared up calling the methods. > Question - Did I set up the class correctly , defining the new object > outside of the class definition ? And would it be better to create an > array (multidimensional) for the composers instead of initializing > each one seperately ? (If this question makes sense) See above. Hope that helps. James Edward G. II ---
**Author:** ![zanoni](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/z/e99b99/32.png) [@zanoni](https://www.ruby-forum.com/u/zanoni)\ **Post date:** [August 15, 2006, 2:16pm UTC](https://www.ruby-forum.com/t/question-on-setting-up-a-class-and-searching-on-objects/102382/3 "2006-08-15T14:16:47Z")
James, Thank you for the explanation and example. Ran through you code in irb so the next step is implementing my method for a search function. Hopefully I will only be back to say I’ve figured it out. No help for now though. Stuart