How to retrieve an array of values from an array of ActiveRecord objects with 'each' method?

Question

I'm trying to perform this non-basic query with Rails :

proj_repartitions = ProjRepartition.includes(:proj_contributions).find( proj_project.proj_charges.each{|pc| pc.proj_repartition_id} )

The point is I need to pass an array of 'ids' to the find method. I want to extract those 'ids' from an array of ActiveRecord objects where each of these is equipped with an 'id' attribute.

When I try on the Rails console:

proj_project.proj_charges.each{|pc| pc.proj_repartition_id}

I got exactly the same array as proj_project.proj_charges

What am I doing wrong?

=== UPDATE ===

According to the answers, my definitive working code is:

proj_project.proj_charges.collect{|pc| pc.proj_repartition_id}

Dave Sexton · Accepted Answer · 2013-03-12 16:20:40Z

1

Instead of using each try map or collect - they should return an array.

answered Mar 12, 2013 at 16:20

Dave Sexton

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2 Comments

Douglas Over a year ago

Great ! It work with 'collect'. I'm still wondering why it doesn't work with each...

Dave Sexton Over a year ago

each is just a way of looping but doesn't return anything whereas collect returns an array. Any chance of a best answer?

Richard Lau · Accepted Answer · 2013-03-12 16:33:11Z

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Each only executes the do block code for each item but doesn't "save" the return value.

Collect and Map executes the do block code for each item and the return value in an array.

hope that makes sense

answered Mar 12, 2013 at 16:33

Richard Lau

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Intrepidd · Accepted Answer · 2013-03-12 16:39:06Z

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proj_project.proj_charges.map(&:proj_repartition_id)

Short way of writing

proj_project.proj_charges.map{|pc| pc.proj_repartition_id}

answered Mar 12, 2013 at 16:39

Intrepidd

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