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shenry

2008-Jul-31 05:38 UTC

difficulty nesting array in hash

Here''s my problem:

I have an array of shipments, each of them has a ship_date

    @shipments = Shipment.find(:all, :order => [''ship_date
ASC''])

I have an array of dates for which I will display scheduled shipments:

    @date_range = (start_date..end_date).to_a

I am trying to create a hash that uses each scheduled date as the key
and whose value is an array of shipments scheduled for that date.

I get the array of scheduled ship dates like this:

    valid_dates = @shipments.collect {|s| s.ship_date}.uniq!

Then proceed to build my nested hash like this:

  @ship_hash = Hash.new{|h,k| h[k]=Hash.new(&h.default_proc) }
    valid_dates.each do |date|
        @ship_hash[date][@shipments.select {|event| event.ship_date =date}]
    end

What this @ship_hash looks like is this:

    {Tue, 29 Jul 2008=>{[#<Shipment_1>, #<Shipment_2>]=>{},
Thur, 31
Jul 2008=>{[#<Shipment_3>]=>{}}}

My code is inserting a blank hash at the end of each value... I don''t
understand Ruby enough to find it after squinting and Googling for
some time. What I''d like it to look like is:

    {Tue, 29 Jul 2008=>[#<Shipment_1>, #<Shipment_2>], Thur, 31
Jul
2008=>[#<Shipment_3>]}

Any help is much appreciated... thanks!

SH


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Frederick Cheung

2008-Jul-31 09:55 UTC

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Re: difficulty nesting array in hash

>
>
> I get the array of scheduled ship dates like this:
>
>    valid_dates = @shipments.collect {|s| s.ship_date}.uniq!
>Warning: uniq! will not always return the uniqued array (since it does  
the modification in place):
[1,2,3].uniq! #=> nil
[1,2,3,3].uniq! #=> [1,2,3]
> Then proceed to build my nested hash like this:
>
>  @ship_hash = Hash.new{|h,k| h[k]=Hash.new(&h.default_proc) }
>    valid_dates.each do |date|
>        @ship_hash[date][@shipments.select {|event| event.ship_date =>
date}]
>    endIsn''t there an assignment missing here? Your hash default proc means  
that saying @ship_hash[date] will create a new empty hash if needed,  
but then did you mean

@ship_hash[date] = @shipments.select {|event| event.ship_date ==date}]

Fred

>
>
> What this @ship_hash looks like is this:
>
>    {Tue, 29 Jul 2008=>{[#<Shipment_1>,
#<Shipment_2>]=>{}, Thur, 31
> Jul 2008=>{[#<Shipment_3>]=>{}}}
>
> My code is inserting a blank hash at the end of each value... I
don''t
> understand Ruby enough to find it after squinting and Googling for
> some time. What I''d like it to look like is:
>
>    {Tue, 29 Jul 2008=>[#<Shipment_1>, #<Shipment_2>], Thur,
31 Jul
> 2008=>[#<Shipment_3>]}
>
> Any help is much appreciated... thanks!
>
> SH
>
>
> >

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shenry

2008-Jul-31 15:04 UTC

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Re: difficulty nesting array in hash

Thanks for the reply, Fred.

I''ll add a condition to check if there are no duplicates in the array
to avoid the uniq! gotcha.

The assignment you suggested worked like a peach. Thanks!

SH
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Frederick Cheung

2008-Jul-31 15:34 UTC

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Re: difficulty nesting array in hash

On 31 Jul 2008, at 16:04, shenry wrote:
>
> Thanks for the reply, Fred.
>
> I''ll add a condition to check if there are no duplicates in the
array
> to avoid the uniq! gotcha.
That wasn''t what I was suggesting. What I meant was that

valid_dates = @shipments.collect {|s| s.ship_date}.uniq
is ok, as is
valid_dates = @shipments.collect {|s| s.ship_date}
valid_dates.uniq!

but
valid_dates = @shipments.collect {|s| s.ship_date}.uniq!

isn''t.

Fred>
>
> The assignment you suggested worked like a peach. Thanks!
>
> SH
> >

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shenry

2008-Jul-31 19:52 UTC

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Re: difficulty nesting array in hash

Understood... clearly I need a Ruby primer (any suggestions?)

Thanks again Fred.

SH

On Jul 31, 8:34 am, Frederick Cheung
<frederick.che...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:> On 31 Jul 2008, at 16:04, shenry wrote:
>
>
>
> > Thanks for the reply, Fred.
>
> > I''ll add a condition to check if there are no duplicates in
the array
> > to avoid the uniq! gotcha.
>
> That wasn''t what I was suggesting. What I meant was that
>
> valid_dates = @shipments.collect {|s| s.ship_date}.uniq
> is ok, as is
> valid_dates = @shipments.collect {|s| s.ship_date}
> valid_dates.uniq!
>
> but
> valid_dates = @shipments.collect {|s| s.ship_date}.uniq!
>
> isn''t.
>
> Fred
>
>
>
> > The assignment you suggested worked like a peach. Thanks!
>
> > SH--~--~---------~--~----~------------~-------~--~----~
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Rails - Jul 2008 - difficulty nesting array in hash

difficulty nesting array in hash

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