Map array elements to hash values Ruby

Question

I have a hash here,

    @property_hash = {
    :code => '',
    :fname => '',
    :lname => '',
    :basic_sal => '',
    :emp_type => '',
}

and an array

line = [02,'Firstname', 'LastName', 5800, 'PL']

I want to map the array into the hash like

@property_hash = {
        :code => 02,
        :fname => 'Firstname',
        :lname => 'LastName',
        :basic_sal => 5800,
        :emp_type => 'PL',
    }

what is the best way to do this ?? Thank you

Can we assume line's order is the same as @property_hash? — Anthony
– Anthony, Commented Apr 19, 2016 at 14:00
In future, consider waiting longer before selecting an answer. Quick selections can discourage other answers and, imo, are discourteous to those still preparing answers (not me). Moreover, the selected answer is sometimes shown to be incorrect (not here). Many here wait at least a couple of hours before awarding the greenie. — Cary Swoveland
– Cary Swoveland, Commented Apr 19, 2016 at 15:34

Thorin · Accepted Answer · 2016-04-19 13:47:16Z

2

you can try like this:

 @property_hash.each_with_index {|(k, v), index| @property_hash[k] = line[index]}

Not best way but that will work

answered Apr 19, 2016 at 13:47

Thorin

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1 Comment

Cary Swoveland Over a year ago

Upvote because this changes the hash in place, which is more efficient than setting @property_hash to a newly-constructed hash. Please remove your last sentence (which is akin to "I'm sure you'll say 'no', but would you go to the dance with me?").

guitarman · Accepted Answer · 2016-04-19 18:00:48Z

2

My solution assumes that line has the same order every time. So I define another array with the field names, merge the corresponding array elements together and convert the result into a hash.

line = [02, 'Firstname', 'LastName', 5800, 'PL']
fields = @property_hash.keys
# => [:code, :fname, :lname, :basic_sal, :emp_type]    


key_value_pairs = fields.zip(line)
# => [[:code, 2], [:fname, "Firstname"], [:lname, "LastName"], [:basic_sal, 5800], [:emp_type, "PL"]]

@property_hash = Hash[key_value_pairs]
# => {:code=>2, :fname=>"Firstname", :lname=>"LastName", :basic_sal=>5800, :emp_type=>"PL"}

edited Apr 19, 2016 at 18:00

answered Apr 19, 2016 at 14:00

guitarman

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4 Comments

SteveTurczyn Over a year ago

As of Ruby 1.9 and onwards, hash entries are ordered by order of creation, so you can now rely on the order being present and consistent.

guitarman Over a year ago

@SteveTurczyn: Thanks for the helpful information. I will edit my answer.

Wand Maker Over a year ago

fields can be written as @property_hash.keys

guitarman Over a year ago

@WandMaker: Yes, you're right. With the information of SteveTurczyn I can do so.

Cary Swoveland · Accepted Answer · 2016-04-19 15:25:26Z

1

Memory-wise, it is more efficient to change @property_hash in place rather than setting @property_hash equal to a newly-constructed hash. Here is one way to that:

lc = line.dup
@property_hash.update(@property_hash) { lc.shift }
  #=> { :code => 02,
        :fname => 'Firstname',
        :lname => 'LastName',
        :basic_sal => 5800,
        :emp_type => 'PL' }

This uses the form of Hash#update (aka merge!) that uses a block to determine the value of keys that are present in both hashes being merged, which here is all of the keys.

answered Apr 19, 2016 at 15:25

Cary Swoveland

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2 Comments

Wand Maker Over a year ago

Nice trick, not sure whether it will be used in real life like this

Cary Swoveland Over a year ago

@Wand, that was my impression when I first saw it, but I've come to rather like it. For one, it returns the updated hash, unlike, for example, h.keys.each { |k| h[k] = lc.shift }.

Wand Maker · Accepted Answer · 2016-04-19 17:18:11Z

1

Here is one more way it can be done:

[@property_hash.keys, line].transpose.to_h

answered Apr 19, 2016 at 17:18

Wand Maker

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1 Comment

Cary Swoveland Over a year ago

More generally, when arrays a and b are the same size, a.zip(b) and [a,b].transpose are interchangeable.

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