# Re: str1 = str2 is not a copy?!?

**URL:** <https://www.ruby-forum.com/t/re-str1-str2-is-not-a-copy/74789>\
**Category:** Ruby\
**Created:** [November 7, 2006, 10:56am UTC](https://www.ruby-forum.com/t/re-str1-str2-is-not-a-copy/74789 "2006-11-07T10:56:27Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![phrogz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/2acd7d/32.png) [@phrogz](https://www.ruby-forum.com/u/phrogz)\
**Post date:** [November 7, 2006, 10:56am UTC](https://www.ruby-forum.com/t/re-str1-str2-is-not-a-copy/74789/1 "2006-11-07T10:56:27Z")

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From: Louis J Scoras [[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)]

> ```
> p array # Doh!!
> 
> x = array ; x[1] = 'win!'
> p array # array has been changed
> 
> ```

The thing to wrap your head around here is that ‘slots’ in an Array, and  
the values in Hash objects, are very much like variables. They point to  
values, they do not contain them.

So breaking down the above:

array = [‘you’, ‘lose’]  
In this case there are three objects: the two strings, and the array.  
The [0] and [1] slots in the array point to those two strings, floating  
out in object space. The variable named ‘array’ is pointing the array  
object floating in space.

a, b = array  
Now, two new variables spring to live, each pointing to those floating  
words. The code “foo = array[1]” is very much like the code “foo = bar”;  
you’re asking Ruby to make the variable ‘foo’ point to whatever the  
array slot/variable bar is pointing to. The ‘a’ and ‘b’ variables have  
nothing to do with the array, except that they happen to be pointing at  
the same objects in space.

b = ‘win’  
Now you’ve just conjured into existence a new object (“win”), and told  
the ‘b’ variable to point to it instead. The [1] slot of the array still  
points at the “lose” object.

x = array  
Here you’re saying “Hey Ruby, please, make the variable ‘x’ point to the  
same thing as the variable ‘array’ is pointing at.”

x[1] = ‘win!’  
Now you’ve made a new object (“win!”) and you’re saying to Ruby, “Hey,  
you know the object that the ‘x’ variable is pointing at? Please ask its  
[1] slot to point at this new “win!” object.”

Because ‘x’ and ‘array’ are both pointing at the same Array object  
floating in space, and one of the slots of that array just changed, they  
are both ‘updated’. (Nothing changes about ‘x’ or ‘array’, but when you  
ask Ruby to inspect the object that either is pointing to, you see the  
same result.)

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<div class="post-metadata">

**Author:** ![phrogz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/2acd7d/32.png) [@phrogz](https://www.ruby-forum.com/u/phrogz)\
**Post date:** [November 7, 2006, 10:56am UTC](https://www.ruby-forum.com/t/re-str1-str2-is-not-a-copy/74789/2 "2006-11-07T10:56:30Z")

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On 11/2/06, Gavin K. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> The thing to wrap your head around here is that ‘slots’ in an Array, and  
> the values in Hash objects, are very much like variables. They point to  
> values, they do not contain them.

Of course. I’m just pointing out how this could be confusing to  
someone who is new to ruby. Same sort of thing with the other thread  
floating around about mutator methods.