Ruby/Rails - How can I add items to an object with each loop iteration

Question

I'm trying to figure ruby out a bit more.....

If I have an object

 @Trees =  Tree.find( :all )

Then make a loop where for each tree I find, add some apples...

 for tree in @trees   
     @apples = Apple.where(:tree_location = > tree.id )
 end

How can I add the additional apples found from each iteration of the loop to the initial object @apples ?

I tried

    @apples = @apples + Apple.where(:tree_location = > tree.id )

but got the error "can't convert Apple into Array"

Thanks for the help .... i'm on a cider deadline lol, corny i know

Gergõ Sulymosi · Accepted Answer · 2011-01-13 23:35:37Z

2

If you want all apples on all the trees, you should have a look at the following query:

@trees =  Tree.find( :all )
@apples = Apple.where(:tree_location => trees.map(&:id))

generates the following sql

select * from apples where tree_location in (... tree ids ...);

it will give you all the apples that belongs to the trees, and costs only two queries instead of n+1

answered Jan 13, 2011 at 23:35

Gergõ Sulymosi

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stef · Accepted Answer · 2011-01-13 22:49:05Z

0

Not quite sure I get you, but...

trees =  Tree.find( :all )
apples = []
trees.each do |tree|
  apples << Apple.where(:tree_location = > tree.id ).to_a
end

apples = apples.flatten.uniq!

puts apples.inspect

answered Jan 13, 2011 at 22:49

stef

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1 Comment

the Tin Man Over a year ago

flatten is because he's doing to_a on Apple.where, resulting in an array of arrays. It's not as effective as other solutions.

coder_tim · Accepted Answer · 2011-01-13 22:53:20Z

0

You might add "all" at the end:

@apples = @apples + Apple.where(:tree_location = > tree.id ).all

answered Jan 13, 2011 at 22:53

coder_tim

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