Ruby: new array from one value in an array of objects

Question

Forgive me if this has already been asked, I couldn't find it.

I have an array of objects, like:

[<#Folder id:1, name:'Foo', display_order: 1>,
<#Folder id:1, name:'Bar', display_order: 2>,
<#Folder id:1, name:'Baz', display_order: 3>]

I'd like to convert that array into an array just of the names, like:

['Foo','Bar','Baz']

and, while I'm at it it would be nice if I could use the same technique down the road to create an array from two of the parameters, ie name and display order would look like:

[['Foo',1],['Bar',2],['Baz',3]]

What's the best 'Ruby Way' to do this kind of thing?

Thanks!

Thanks for the many answers! htanata's was the most complete. — Andrew
– Andrew, Commented Mar 4, 2011 at 16:00

htanata · Accepted Answer · 2015-08-05 18:52:12Z

16

How about these?

# ['Foo','Bar','Baz']
array = folders.map { |f| f.name }
# This does the same, but only works on Rails or Ruby 1.8.7 and above.
array = folders.map(&:name)

# [['Foo',1],['Bar',2],['Baz',3]]
array = folders.map { |f| [f.name, f.display_order] }

edited Aug 5, 2015 at 18:52

answered Mar 4, 2011 at 15:48

htanata

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1 Comment

pilcrow Over a year ago

To clarify, f.map(&:name) works without Rails in 1.8.7 and (at least) 1.9.2.

Andrew Grimm · Accepted Answer · 2011-03-06 22:24:55Z

3

How about:

a.collect {|f| f.name}

edited Mar 6, 2011 at 22:24

Andrew Grimm

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answered Mar 4, 2011 at 15:45

grifaton

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1 Comment

Simon Woker Over a year ago

or use a.collect! if you really want to replace it. For the second question: Hust extend it a bit to a.collect{|f| [f.name, f.display_order]}

Mauricio · Accepted Answer · 2011-03-04 15:48:21Z

0

You can do

array.map { |a| [a.name, a.display_order] }

answered Mar 4, 2011 at 15:48

Mauricio

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Comments

Fernando Diaz Garrido · Accepted Answer · 2011-03-04 15:49:20Z

0

To get ['Foo','Bar','Baz'] , you can do: array.map(&:name)

For the second one you could use array.map {|a| [a.id, a.name] }

answered Mar 4, 2011 at 15:49

Fernando Diaz Garrido

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