Copy a 2-D array to another array in Ruby

Question

I have a statement like this in Ruby:

@mastertest = connection.execute("select code_ver from mastertest")

So now I want to make a copy of this 2-D array, because if I do something like @temp = @mastertest, it makes changes to @mastertest when I make any changes to @temp.

I tried using the following:

@temp = Marshal.load(Marshal.dump(@mastertest))

But this gives me an error saying "no marshal_dump is defined for class Mysql2::Result". So I am assuming that the @mastertest is of some other type than a 2-D array.

Can someone help me how to make a copy of this array?

halfelf · Accepted Answer · 2012-10-17 10:07:13Z

1

There are two ways to work here: (dup or clone isn't fully deep copy, only Marshal does).

Use Object#dup or clone. Try @temp = @mastertest.dup. I don't know the format of Mysql2::Result, so this way may fail when it is like a "2-D array", which you have to dup each element in the Enumerable-mixed class. The dup method just calls initialize_copy for that class. If there is anything not POD(plain-old-data) in an array-like object, it will only make a shallow copy for it.
Write your monkey patch for Mysql2::Result with two methods: marshal_dump and marshal_load. This will make it respond to Marshal.dump. See the doc about Marshal here.

edited Oct 17, 2012 at 10:07

answered Oct 17, 2012 at 9:42

halfelf

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Soundar Rathinasamy · Accepted Answer · 2012-10-17 09:50:49Z

0

Try

@temp = @mastertest.clone

Now changes to @temp will not affect the @mastertest

answered Oct 17, 2012 at 9:50

Soundar Rathinasamy

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halfelf Over a year ago

This will not work for something like 2-D array. For example, a = [[1,2]] b = a.dup a[0] << 3 puts b.

Pi Horse · Accepted Answer · 2012-10-19 18:16:04Z

0

I managed to solve this by using the following:

@new_array = Array.new
@mastertest.each { |r| @new_array.push(r[0]) }

answered Oct 19, 2012 at 18:16

Pi Horse

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