String.insert newbie question


#1

Hello,

I’ve only been checking out Ruby for a couple of days, but today I came
across this problem.

If I do this:

#!/usr/bin/env ruby -w

string1 = “abc”
string2 = string1

string2.insert(-1, “def”)

puts string1
puts string2

Then the result is:

abcdef
abcdef

How come string1 gets changed?!?

Thanks,

Marco


#2

On 1/26/07, Marco G. removed_email_address@domain.invalid wrote:

string1 = “abc”
abcdef

check it out in irb.

irb(main):001:0> string1 = “abc”
=> “abc”
irb(main):002:0> string2 = string1
=> “abc”
irb(main):003:0> string2.object_id
=> 23129580
irb(main):004:0> string1.object_id
=> 23129580

Hope that helps.


#3

On 1/27/07, Marco G. removed_email_address@domain.invalid wrote:

Jason M. wrote:

check it out in irb.

Hope that helps.

Thanks for clearing that up, didn’t know about object_id. Is this
behaviour common in programming languages? Seems weird to me.

It’s not weird if you consider :

customer0 = Customer.new(“John”, “Doe”)
customer1 = customer0
customer0.first_name = “Paul”
puts customer1.first_name

customer0 and customer1 points to the same instance.

Java strings are misleading.

Best regards,


#4

Jason M. wrote:

check it out in irb.

Hope that helps.

Thanks for clearing that up, didn’t know about object_id. Is this
behaviour common in programming languages? Seems weird to me.

Then again I’m very new to all of this.

This means I could do

string1 = “abc”
string2 = string1
string3 = string2
string4 = string3

and they all will change if I change string 4. What can I do to keep
string1 stay the same even if I change string 4?


#5

John M. wrote:

customer0 = Customer.new(“John”, “Doe”)
customer1 = customer0
customer0.first_name = “Paul”
puts customer1.first_name

customer0 and customer1 points to the same instance.

Yes, that makes sense. I’ve even found a much simpler solution to my
original problem that makes the question irrelevant.

Thanks, everyone!


#6

Hi!

On Jan 27, 2007, at 04:40, Marco G. wrote:

Yes, that makes sense. I’ve even found a much simpler solution to my
original problem that makes the question irrelevant.

Thanks, everyone!

I would like to notice, that if you ever need two separate objects, you
can always use a dup method, e.g:

string2 = string1.dup # Will have two different string instances

Your sincerely,
Damian/Three-eyed Fish


#7

Thanks very, very much, I was mired in a problem with this and you’ve
rescued me.
Bill M.
Eloqua

Damian T. wrote:

Hi!

I would like to notice, that if you ever need two separate objects, you
can always use a dup method, e.g:

string2 = string1.dup # Will have two different string instances

Your sincerely,
Damian/Three-eyed Fish