Sorting an ActiveRecord hash

Rails
1

I’ve got a query like the following:

@tags = Tag.find(:all, :limit => 20, :conditions => “id != 22 and id !=
47” , :order => “count DESC”)

My understanding is the ActiveRecord returns an array of hash objects to
@tags. so @tags is actually an array full of hashes.

the tags table has the following fields:

id, name, count, updated_at

The query returns the top 20 tags sorted by count into @tags

How can I then sort @tags by the ‘name’ field so I will have the top 20
tags sorted by alpha name?

2

:order => ‘name’

3

nuno wrote:

:order => ‘name’

not sure what you mean. I’m already doing :order => ‘count DESC’ so I
can get the tags with the highest count.

4

Jamey C. wrote:

the tags table has the following fields:

@tags.sort! { |t| t.name }

Oops. That should be:

@tags.sort! { |a,b| a.name <=> b.name }

or, alternatively:

sorted_tags = @tags.sort_by { |t| t.name }

Jamey

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5

Jamey C. wrote:

Jamey C. wrote:

the tags table has the following fields:

@tags.sort! { |t| t.name }

Oops. That should be:

@tags.sort! { |a,b| a.name <=> b.name }

or, alternatively:

sorted_tags = @tags.sort_by { |t| t.name }

excellent. thanks for the help Jamey. I was trying

@tags.sort! { |t| t.name }

myself already and getting errors. I didn’t realize I needed to use the
<=> syntax.

6

Craig J. wrote:

id, name, count, updated_at

The query returns the top 20 tags sorted by count into @tags

How can I then sort @tags by the ‘name’ field so I will have the top 20
tags sorted by alpha name?

@tags.sort! { |t| t.name }

Confidentiality Notice: This email message, including any attachments,
is for the sole use of the intended recipient(s) and may contain
confidential and/or privileged information. If you are not the intended
recipient(s), you are hereby notified that any dissemination,
unauthorized review, use, disclosure or distribution of this email and
any materials contained in any attachments is prohibited. If you receive
this message in error, or are not the intended recipient(s), please
immediately notify the sender by email and destroy all copies of the
original message, including attachments.

7

On Friday 01 December 2006 16:28, Craig J. wrote:

I’ve got a query like the following:

@tags = Tag.find(:all, :limit => 20, :conditions => “id != 22 and id
!= 47” , :order => “count DESC”)

My understanding is the ActiveRecord returns an array of hash objects
to @tags. so @tags is actually an array full of hashes.

No! Look for yourself by looking at @tags, e.g. by executing the query
in script/console.

How can I then sort @tags by the ‘name’ field so I will have the top
20 tags sorted by alpha name?

Arguably, tags have a natural ordering by name, therefore it makes sense
for Tag to implement <=>

class Tag
def <=>(other)
self.name <=> other.name
end
end

Then you can just call @tags.sort! and the supplied operator is used.
For good measure you should make Tag Comparable to get a few more
methods for free

class Tag
include Comparable # provides <, <=, ==, >=, >, between?
def <=>(other)
self.name <=> other.name
end
end

Even better, push back the query into your Tag model class. Thus,

@tags = Tag.find(:all, :limit => 20, :conditions => “id != 22 and id
!= 47” , :order => “count DESC”)

becomes

class Tag
def Tag.find_top_20(*excluded_ids)
exclude_ids_condition = excluded_ids.empty? ?
nil :
[‘id NOT IN (?)’, excluded_ids]
tags = Tag.find(:all,
:limit => 20,
:conditions => exclude_ids_condition,
:order => ‘count DESC’)
tags.sort!
end
end

Presumably the excluded ids have some meaning and you really shouldn’t
carry them around by hand. Very probably, what you’re trying to do
belongs as an extension on an association – have a good look at the
docs for associations.

Michael

–
Michael S.
mailto:[email protected]
http://www.schuerig.de/michael/

8

Craig J. wrote:

nuno wrote:

:order => ‘name’

not sure what you mean. I’m already doing :order => ‘count DESC’ so I
can get the tags with the highest count.

Sorry, I did read your question the wrong way !

I wonder if there is a full SQL solution that would be faster than the
ruby sort…

9

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Craig J. wrote:

sorted_tags = @tags.sort_by { |t| t.name }

excellent. thanks for the help Jamey. I was trying

@tags.sort! { |t| t.name }

You can use this with sort_by:

@tags = @tags.sort_by{ |t| t.name }

There is no “sort_by!” method though.

http://www.ruby-doc.org/core/classes/Enumerable.html#M003156

Zach
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10

How about:

@tags = Tag.find(:all, :limit => 20, :conditions => “id != 22 and id !=
47” , :order => “count DESC, name”)

I do not have a test environment for this at hand, but depeneding on
your database it should be possible.

http://dev.mysql.com/doc/refman/4.1/en/order-by-optimization.html