Create hash from variables in loop

Question

I want to end up with an array of hashes.

I am starting with an array of codes:

@codes = ['123', '456', '789']

I take each of those codes and hit an API with them and it returns values that I parse into variables in a loop, like so:

@codes.each do |x|
  @y = x.get_some_data
  @brand = @y[brand]
  @size = @y[size]
end

Then I want to put this data into an array of hashes

merged_array = []
final_hash = @codes.map{|code| {:code => code, :brand=> @brand, :size=> @size}
merged_array << final_hash

And in a perfect world, end up with hashes that look like this in the merged_array:

 {:code => '123', :brand=> 'nike', :size=> 8 }
 {:code => '456', :brand=> 'adidas', :size=> 4 }
 {:code => '789', :brand=> 'converse', :size=> 10 }

But when I run my script it maps the codes right, but overwrites the @brand, @size variables and just returns the values of the last loop.

Not sure how to get all my variables into the hashes?

instead of the codes.each section just put all this logic directly in the map method also probably no need for instance variables since you will just discard this data anyway. — engineersmnky
– engineersmnky, Commented Jun 8, 2015 at 14:23

Technaton · Accepted Answer · 2015-06-08 15:52:00Z

5

In your code example, the variables are all declared as being instance variables, because they're prefixed with @.

However, the variables within the loop are simply working/temporary variables, not instance variables. Additionally, x.get_some_data is probably not working, since x is just the loop variable and contains 456, abc, etc., and not an object with the desired method. Thus, the following code should produce your desired result:

def get_data(codes)
  result = []
  codes.each do |code|
    y = get_some_data(code)
    result << {
      code: code,
      brand: y['brand'],
      size: y['size']
    }
  end
  result
end

This is a very verbose example; you can put the whole logic in map, if the return value of get_some_data permits it.

A more elegant version would utilize Enumerable#each_with_object (the Array class includes Enumereable):

def get_data(codes)
  codes.each_with_object([]) do |code, result|
    y = get_some_data(code)
    result << {
      code: code,
      brand: y['brand'],
      size: y['size']
    }
  end
end

Thanks, Cary Swoveland, for pointing this out!

edited Jun 8, 2015 at 15:52

answered Jun 8, 2015 at 14:25

Technaton

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3 Comments

ToddT Over a year ago

arghhhhh.. the answer was really your very first line.. instance vs. temp variables.. I changed them to the method/temp variables and everything is working fine now.. wow.. easy fix but I just didn't see it!! thanks so much

Cary Swoveland Over a year ago

A small suggestion: instead of result = [] at the beginning and result at the end, codes.each_with_object([]) { |code, result|....

Technaton Over a year ago

Good idea, @CarySwoveland, I've edited my answer accordingly.

Abhi · Accepted Answer · 2017-09-18 14:32:47Z

1

This should do the work

@codes.map{|code| {:code => code, :brand => code.get_some_data['brand'], code.get_some_data['size']}}

But, I'm really not sure what String.get_some_data will give you. Eg:- '123'.get_some_data['brand']

edited Sep 18, 2017 at 14:32

answered Jun 8, 2015 at 14:31

Abhi

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