Removing empty hashes {} from array in Active Model Serialized object - ruby-on-rails

Question

I have a few conditions where don't want to serialize the current object and want to skip it. But i haven't found a way to do that so I am ignoring attributes on attribute :foo, if: :condition. And this is generating empty {} in my serialized object inside arrays. How do I fix this?
[
{
"id": 392027,
"name": "ISC Board",
"grades":[
{
"id": 333938,
"name": "1",
"subjects": [
{
"id": 571671,
"subject": "Math"
},
{
"id": 742980,
"subject": "Science"
},
{
"id": 186926,
"subject": "English"
},
{
"id": 658224,
"subject": "Social_Studies"
},
{},
{},
{}
]
},
{
"id": 333943,
"name": "2",
"subjects": [
{
"id": 571671,
"subject": "Math"
},
{
"id": 742980,
"subject": "Science"
},
{
"id": 186926,
"subject": "English"
},
{
"id": 658224,
"subject": "Social_Studies"
},
{},
{},
{}
]
},
]
},
{
"id": 666627,
"name": "NY Board",
"grades":[
{
"id": 333938,
"name": "1",
"subjects": [
{
"id": 571671,
"subject": "Math"
},
{
"id": 742980,
"subject": "Science"
},
{
"id": 186926,
"subject": "English"
},
{
"id": 658224,
"subject": "Social_Studies"
},
{},
{},
{}
]
},
{
"id": 432943,
"name": "2",
"subjects": [
{
"id": 571671,
"subject": "Math"
},
{
"id": 742980,
"subject": "Science"
},
{
"id": 186926,
"subject": "English"
},
{
"id": 658224,
"subject": "Social_Studies"
},
{},
{},
{}
]
},
]
}
]
serializer looks something like this-
class BoardSerializer < ActiveModel::Serializer
#some code
class GradeSerializer < ActiveModel::Serializer
has_many :subjects
#some code
class SubjectSerializer < ActiveModel::Serializer
attribute :id, if: :condition
attribute :name, key: :subject, if: :condition
def condition
#some code
#returns true or false
#will not return both :id and :subject if false- I want to
#skip this current object if condition fails. (returns {})
end
end
end
end
How do I simply skip the current object in the serializer or remove empty hashes? Thanks

Answer 1

Please, check if this is the expected result:
input.transform_values { |v| v.map {|e| e.transform_values { |vv| vv.class == Array ? vv.select { |ee| ee unless ee.empty? } : vv } } }
# => {:grades=>[{:id=>333938, :name=>"1", :subjects=>[{:id=>571671, :subject=>"Math"}, {:id=>742980, :subject=>"Science"}, {:id=>186926, :subject=>"English"}, {:id=>658224, :subject=>"Social_Studies"}]}]}
EDIT: to meet changes in OP question.
input.map { |e| e.transform_values { |v| v.is_a?(Array) ? v.map {|ee| ee.transform_values { |vv| vv.is_a?(Array) ? vv.select { |eee| eee unless eee.empty? } : vv } } : v } }
# => [{:id=>392027, :name=>"ISC Board", :grades=>[{:id=>333938, :name=>"1", :subjects=>[{:id=>571671, :subject=>"Math"}, {:id=>742980, :subject=>"Science"}, {:id=>186926, :subject=>"English"}, {:id=>658224, :subject=>"Social_Studies"}]}, {:id=>333943, :name=>"2", :subjects=>[{:id=>571671, :subject=>"Math"}, {:id=>742980, :subject=>"Science"}, {:id=>186926, :subject=>"English"}, {:id=>658224, :subject=>"Social_Studies"}]}]}, {:id=>666627, :name=>"NY Board", :grades=>[{:id=>333938, :name=>"1", :subjects=>[{:id=>571671, :subject=>"Math"}, {:id=>742980, :subject=>"Science"}, {:id=>186926, :subject=>"English"}, {:id=>658224, :subject=>"Social_Studies"}]}, {:id=>432943, :name=>"2", :subjects=>[{:id=>571671, :subject=>"Math"}, {:id=>742980, :subject=>"Science"}, {:id=>186926, :subject=>"English"}, {:id=>658224, :subject=>"Social_Studies"}]}]}]

Answer 2

You can use #select! for this matter:
input = {
"grades":
[
{
"id": 333938,
"name": "1",
"subjects":
[
{
"id": 571671,
"subject": "Math"
},
{
"id": 742980,
"subject": "Science"
},
{
"id": 186926,
"subject": "English"
},
{
"id": 658224,
"subject": "Social_Studies"
},
{},
{},
{}
]
}
]
}
input[:grades].first[:subjects].select! { |i| !i.empty? }