# What is the error in this program

**URL:** <https://www.ruby-forum.com/t/what-is-the-error-in-this-program/140483>\
**Category:** Ruby\
**Created:** [June 14, 2008, 8:44pm UTC](https://www.ruby-forum.com/t/what-is-the-error-in-this-program/140483 "2008-06-14T20:44:24Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![graphicmist](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/c0e974/32.png) [@graphicmist](https://www.ruby-forum.com/u/graphicmist)\
**Post date:** [June 14, 2008, 8:44pm UTC](https://www.ruby-forum.com/t/what-is-the-error-in-this-program/140483/1 "2008-06-14T20:44:24Z")

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class Customer  
@@no\_of\_customers=0

def initialize(id, name, addr)  
@id=id  
@name=name  
@addr=addr  
end

def display\_details()  
puts “Customer ID #@id”  
puts “Customer Name #@name”  
puts “Customer Address #@addr”  
@@no\_of\_customers+=1  
end

def total\_customers  
puts “total no. of customers are #@@no\_of\_customers”  
end  
end

while($\_!=“n”)  
index=0;  
print "Enter user id "  
id=gets  
chomp  
print "Enter user name "  
name=gets  
chomp  
print "Enter user address "  
addr=gets  
chomp  
cust=Array.new  
cust[index]=Customer.new(id,name,addr)  
index+=1  
print "do you want to enter more data y/n "  
gets  
chomp  
end

0.upto(index-1) do |c|  
puts cust[c].display\_details()  
end

Whenever i run this program and provide the input the display\_details  
function show the details of only the last customer.

---

<div class="post-metadata">

**Author:** ![graphicmist](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/c0e974/32.png) [@graphicmist](https://www.ruby-forum.com/u/graphicmist)\
**Post date:** [June 14, 2008, 8:54pm UTC](https://www.ruby-forum.com/t/what-is-the-error-in-this-program/140483/2 "2008-06-14T20:54:59Z")

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Manish Kutaula wrote:

> while($\_!=“n”)  
> Â index=0;  
> Â […]  
> Â index+=1  
> Â […]  
> Â end

You set index to 0 at every iteration of the loop.

HTH,  
Sebastian

---

<div class="post-metadata">

**Author:** ![graphicmist](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/c0e974/32.png) [@graphicmist](https://www.ruby-forum.com/u/graphicmist)\
**Post date:** [June 14, 2008, 10:17pm UTC](https://www.ruby-forum.com/t/what-is-the-error-in-this-program/140483/3 "2008-06-14T22:17:23Z")

</div>

On Sat, Jun 14, 2008 at 2:53 PM, Sebastian H. \<  
removed\_email\_address@domain.invalid\> wrote:

> You set index to 0 at every iteration of the loop.

Yes, but beyond that here’s a critique of this code in the way of a  
refactoring:

class Customer  
@@no\_of\_customers=0 # I personally wouldn’t use a class variable  
here,  
but I’ll let it go.

def initialize(id, name, addr)  
@id=id  
@name=name  
@addr=addr  
# If we are really counting customers we should do it  
# when they each customer is created  
# not when they are displayed since  
# a customer just might get displayed more than once  
# or not at all.  
@@no\_of\_customers+=1  
end

def display\_details()  
puts “Customer ID #@id”  
puts “Customer Name #@name”  
puts “Customer Address #@addr”  
end

# I’d make this a class method since the number of customers

# is a property of the class rather than each instance.

def self.total\_customers  
puts “total no. of customers are #@@no\_of\_customers”  
end  
end

# This was just too C/Fortran like, let’s treat the array like

# an object, not just a static array!

# 

# Since we’re collecting the customers here,

# we need to instantiate the array once, not everytime

# through the loop, and let’s use a clearer name:

customers = []

# Let’s lose the magic variable $\_! and make this a

# bit more understandable

more = “y”

# note also that this was $\_! = “n” which is an assignment

# NOT a comparison

until(more == “n”)  
print "Enter user id "

# We need to send chomp to the string we got, not self!

id=gets chomp  
print "Enter user name "  
name=gets chomp  
print "Enter user address "  
addr=gets chomp

# Let the array keep track of how many elements it has

customers \<\< Customer.new(id,name,addr)  
print "do you want to enter more data y/n "  
more = gets chomp  
end

# And using each is much less bug prone than a C/Basic/Fortran-like

loop:  
customers.each do |customer|  
puts customer.display\_details()  
end

I note that this code doesn’t actually use the total\_customers method,  
with  
the change I made this would be done with

puts Customer.total\_customers

However if the real requirement is to get the number of Customers we  
processed in the loop, then we can  
do away with the counter and the class method and just use

puts customers.length

–  
Rick DeNatale

My blog on Ruby  
[http://talklikeaduck.denhaven2.com/](http://talklikeaduck.denhaven2.com/)