Return ActiveRecord query as variable, not hash?

Question

I am doing an ActiveRecord find on a model as such

@foo = MyModel.find(:all, :select => 'year')

As you can see, I only need the year column from this, so my ideal output would be

["2008", "2009", "2010"]

Instead, though, I get an a hash of the models, with each one containing the year, as such:

[#<MyModel year: "2008">, #<MyModel year: "2009">, #<MyModel year: "2010">]

I can loop through it as such to convert it to my ideal output:

@years = []
for bar in @foo
    @years.push(bar.year)
end

but is there a way to retrieve this result to begin with? (i.e. without going through the extra processing?). If there is not, what is a more concise way to do this processing?

Thank you.

jigfox · Accepted Answer · 2010-06-28 18:22:13Z

4

try:

@foo = MyModel.find(:all, :select => 'year').map(&:year)

You also can call .uniq() on the result to remove duplicates.

@foo = MyModel.find(:all, :select => 'year').map(&:year).uniq

This is the short form for

@foo = MyModel.find(:all, :select => 'year').map{ |model| model.year }

This loops over the MyModel Array and crates a new array of the return values with in the block (model.year).

or even shorter code, but first calling everything from db:

@foo = MyModel.all.map(&:year)

edited Jun 28, 2010 at 18:22

answered Jun 28, 2010 at 18:06

jigfox

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1 Comment

Yuval Karmi Over a year ago

Could you explain this please?

François Beausoleil · Accepted Answer · 2010-06-28 20:18:09Z

1

If you don't want to instantiate models, you'd do it this way:

MyModel.connection.select_values("SELECT year FROM my_models")

This will return an Array of String objects. Then you can transform using Ruby tools as you see fit.

answered Jun 28, 2010 at 20:18

François Beausoleil

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Comments

hundredwatt · Accepted Answer · 2010-06-28 18:22:42Z

0

You can use map to change every value in an array. Example:

@foo = MyModel.find(:all, :select => 'year').map { |model_object| model_object.year }

edited Jun 28, 2010 at 18:22

answered Jun 28, 2010 at 18:10

hundredwatt

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1 Comment

jigfox Over a year ago

you need to put a dot between 'year') and map!, and why do you use map!, map would just work fine here, because your assigning the result to a new variable

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