Merge a single array into nested array in rails - ruby-on-rails

Question

I have a list of objects something like this:
a = [
{
id: 0,
name: "ABC",
work: "ABC2"
},
{
id: 0,
name: "XYZ",
work: "XYZ2"
},
{
id: 1,
name: "ACD",
work: "ACD2"
}
]
And I want to convert it into something like this:
b = [
{
id: 0,
fields: [
{
name: "ABC",
work: "ABC2"
},
{
name: "XYZ",
work: "XYZ2"
}
]
},
{
id: 1,
fields: [
{
name: "ACD",
work: "ACD2"
}
]
}
]
The idea is to group the objects (by id) in one array.
The approach I tried is:
b = []
rest_object = []
a.each_with_index do |aa, idx|
aa.delete(:id)
rest_object << aa
if idx == 0
next
end
puts a[idx][:id], a[idx-1][:id]
if a[idx][:id] != a[idx-1][:id]
b << {id: a[idx-1][:id], names: rest_object}
rest_object = []
end
end
But I am getting an empty output.
Also, if it is possible to achieve the same in some cleaner way.
That would be helpful.

Answer 1

Something like this does the job. This deletes the :id key-value pair from each hash and uses the value to group the remainder of the hash. Then map the resulting hash to created an array and transform the data into {id: ..., fields: ...} format.
a = [{id: 0, name: "ABC", work: "ABC2"}, {id: 0, name: "XYZ", work: "XYZ2"}, {id: 1, name: "ACD", work: "ACD2"}]
b = a.group_by { |hash| hash.delete(:id) }
.map { |id, fields| {id: id, fields: fields} }
#=> [{:id=>0, :fields=>[{:name=>"ABC", :work=>"ABC2"}, {:name=>"XYZ", :work=>"XYZ2"}]}, {:id=>1, :fields=>[{:name=>"ACD", :work=>"ACD2"}]}]
Note: This mutates the hashes in the a array. If you don't want this change a.group_by to a.map(&:dup).group_by. Which first duplicates all hashes before doing any mutations.

Answer 2

Try following,
required_keys = a[0].except(:id).keys
b = a.group_by { |x| x[:id] }
b = b.inject([]) do |m,(k,v)|
arr = { id: k }
required_keys.each do |key|
arr[key.to_s.pluralize.to_sym] = v.map { |z| z.slice(key) }
end
m << arr
end
# => [{:id=>0, :names=>[{:name=>"ABC"}, {:name=>"XYZ"}]}, {:id=>1, :names=>[{:name=>"ACD"}]}]

Answer 3

a = [
{
id: 0,
name: "ABC"
},
{
id: 0,
name: "XYZ"
},
{
id: 1,
name: "ACD"
}
]
ary = []
a.each do|val|
ary[val[:id]] = {id: val[:id]} unless ary[val[:id]]
ary[val[:id]][:names] = [] unless ary[val[:id]][:names]
ary[val[:id]][:names].push({name: val[:name]})
end

Answer 4

If I understand, given a more general array like this:
a = [ { id: 0, name: "ABC", etc: "01" },
{ id: 0, name: "XYZ", etc: "02" },
{ id: 1, name: "ACD", etc: "11" } ]
The first idea I came up with is doing something like this:
require 'active_support/inflector' # for using pluralize
res = a.group_by{ |h| h[:id] }.values.map do |ary|
h = Hash.new{ |h,k| h[k] = [] }
ary.each { |hh| hh.each { |k,v| h[k] << v } }
h[:id] = h[:id].first
h.transform_keys do |k|
unless k == :id
k.to_s.pluralize.to_sym
else
k
end
end
end
res #=> [{:id=>0, :names=>["ABC", "XYZ"], :etcs=>["01", "02"]}, {:id=>1, :names=>["ACD"], :etcs=>["11"]}]
This is not exactly the format you require, but to get that format, just change this line
ary.each { |hh| hh.each { |k,v| h[k] << v } }
to
ary.each { |hh| hh.each { |k,v| h[k] << { k => v } } }