creating dynamic hash with key and value in ruby on rails

Question

I am trying to create Hash with dynamic key and respective values. For example like this

hash = {1 => 23.67, 1 => 78.44, 3 => 66.33, 12 => 44.2}

Something like this in which 1,2,12 are array index. I hope it is understandable. I am trying with the syntax from ROR tutorials.

Like this

 test = Hash.new 

  for i in 0..23
   if (s.duration.start.hour == array[i].hour)
     s.sgs.each do |s1|
       case s1.type.to_s
       when 'M'
         test ={i => s1.power} # here I am trying to create hash like give example in which i is for loop value
       when 'L'
         puts "to be done done"
       else
         puts "Not Found"
       end
     end
   end
 end
end

Updated code

 test = Hash.new
 for i in 0..23
   if (s.duration.start.hour == array[i].hour)
     s.sgs.each do |s1|
       case s.type.to_s
       when 'M'
         puts s1.power;
         test[i] =  s1._power
       when 'L'
         puts "to be done"
       else
         puts "Not  Found"
       end
     end
   end
 end

Results

on traversing

for t in 0..array.size
  puts test[t]
end

Results :

t = 68.6 # which is last value

and expected

t = 33.4
t = 45.6 etc

Sample logs

after assign {23=>#<BigDecimal:7f3a1e9a6870,'0.3E2',9(18)>}
before assign {23=>#<BigDecimal:7f3a1e9a6870,'0.2E2',9(18)>}
after assign {23=>#<BigDecimal:7f3a1e9ce550,'-0.57E2',9(18)>}
before assign {23=>#<BigDecimal:7f3a1e9ce550,'-0.57E2',9(18)>}

if any other optimised solution is there would be good thanks

Uri Agassi · Accepted Answer · 2014-06-01 12:55:35Z

10

You are re-assigning test with a new hash on each iteration. You should add to it, so instead of

test ={i => s1.power}

you should do:

test[i] = s1.power

This sets the value of key i to s1.power

If you want to keep an array of all the values for a given key, I would suggest the following (more ruby-ish) solution:

hour_idx = array.find_index { |item| s.duration.start.hour == item.hour }

values = case s.type.to_s
  when 'M'
    s.sgs.map(&:_power)
  when 'L'
    puts "to be done"
  else
    puts "Not  Found"
  end

test = { hour_idx => values }

What I'm doing here is:

Find the hour_idx which is relevant to the current s (I assume there is only one such item)
Create an array of all the relevant values according to s.type (if it is 'M' an array of all the _power of s.sgs, for 'L' whatever map you need, and nil otherwise)
Create the target hash using the values set in #1 and #2...

edited Jun 1, 2014 at 12:55

answered Jun 1, 2014 at 11:55

Uri Agassi

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6 Comments

JNI_OnLoad Over a year ago

but When I am checking length for it, it shows only 1 but it goes in this switch case more then that...i Think it is something related to initialization of Hash with Hash.new

Uri Agassi Over a year ago

Have you made the change I've suggested? your original code does not add keys, it simply creates a new hash of size 1 each time, and overrides the previous hash...

JNI_OnLoad Over a year ago

yes, I did as you mention, i checked it just now, it overriding values and keeping last one only....

Uri Agassi Over a year ago

Also expected result vs actual result

Uri Agassi Over a year ago

Add some logs to your iteration: puts "before assign #{test}" before the test[i] = ... line, and puts "after assign #{test}" after that line

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