This is my array
[{:amount=>10, :gl_acct_id=>1, :alt_amount=>20}, {:amount=>20, :gl_acct_id=>2
, :alt_amount=>30}]
i want result
[{:amount => 30}] or {:amount = 30}
Any idea?
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8 Answers
Ruby versions >= 2.4.0 has an Enumerable#sum method. So you can do
arr.sum {|h| h[:amount] }
3 Comments
Anton Semenichenko
probably the best answer IMHO
tvw
But this returns 30 and not the desired result [{:amount => 30}] or {:amount = 30}
Santhosh
@tvw Which is trivial once you get the sum. Also this answer was posted 6 years after OP had asked the question. So my intension was to help any one who comes here with a similar problem. :)
array.map { |h| h[:amount] }.sum
You can use inject to sum all the amounts. You can then just put the result back into a hash if you need to.
arr = [{:amount=>10, :gl_acct_id=>1, :alt_amount=>20}, {:amount=>20, :gl_acct_id=>2, :alt_amount=>30}]
amount = arr.inject(0) {|sum, hash| sum + hash[:amount]} #=> 30
{:amount => amount} #=> {:amount => 30}
2 Comments
BenKoshy
thank you @sepp2k this is very useful. in the answer above we have to name the key - what if we want the sum for all the keys - (i.e. we don't want to name them individually - do you know how we would solve that?)
Steven Moffat
I have the same issue, my hash is [2, #<BigDecimal:7f29fe6164b0,'0.1256E4',9(18)>, 4, #<BigDecimal:7f29fe6163e8,'0.281E4',9(18)>, 3, #<BigDecimal:7f29fe6162a8,'0.24E4',9(18)>] and I wish to sum the values which have no name.
This is one way to do it:
a = {amount:10,gl_acct_id:1,alt_amount:20},{amount:20,gl_acct_id:2,alt_amount:30}
a.map {|h| h[:amount] }.reduce(:+)
However, I get the feeling that your object model is somewhat lacking. With a better object model, you would probably be able to do something like:
a.map(&:amount).reduce(:+)
Or even just
a.sum
Note that as @sepp2k pointed out, if you want to get out a Hash, you need to wrap it in a Hash again.
3 Comments
krunal shah
@mittag can you tell me what should be a better object model ?? so i can use this one ... a.map(&:amount).reduce(:+)
sepp2k
@krunal: Most basic example:
Foo = Struct.new(:amount, :gl_acct_id, :alt_amount); a = [Foo.new(10, 1, 20), Foo.new(20,2,30)]; a.map(&:amount).inject(:+) #=> 30
Jörg W Mittag
@sepp2k: Thanks! Missed that one.
why not pluck?
ary = [{:amount=>10, :gl_acct_id=>1, :alt_amount=>20}, {:amount=>20, :gl_acct_id=>2, :alt_amount=>30}]
ary.pluck(:amount).sum
# for more reliability
ary.pluck(:amount).compact.sum
2 Comments
silva96
Only rails thought, from 5.0 and above api.rubyonrails.org/classes/Enumerable.html#method-i-pluck
Allison
This would require unnecessarily iterating over the array several times
[{
:amount=>10,
:gl_acct_id=>1,
:alt_amount=>20
},{
:amount=>20,
:gl_acct_id=>2,
:alt_amount=>30
}].sum { |t| t[:amount] }
2 Comments
Nissa
Welcome to Stack Overflow! It's usually better to explain your answers, rather than just posting code.
Toby Speight
Welcome to Stack Overflow! Although this code may help to solve the problem, it doesn't explain why and/or how it answers the question. Providing this additional context would significantly improve its long-term educational value. Please edit your answer to add explanation, including what limitations and assumptions apply.
If we are having only a single element in all the hashes in a array and also keys were different ?
Here is the solution I found:
Sum of the values:
x = [{"a" => 10},{"b" => 20},{"d" => 30}]
Solution:
x.inject(0){|sum, hash| sum+= hash.values.join.to_i }
Also we can do:
x.inject(0){|sum, hash| sum+= hash.values.sum }
Comments
total=0
arr = [{:amount=>10, :gl_acct_id=>1, :alt_amount=>20}, {:amount=>20, :gl_acct_id=>2, :alt_amount=>30}]
arr.each {|x| total=total+x[:amount]}
puts total
1 Comment
Andrea Pavoni
that is mostly equivalent to this one-liner:
total = arr.inject(0) {|sum, hash| sum += hash[:amount]}