I have a Ruby array of students. Student class has attributes id, name and age.
students = [
{id:"id1",name:"name1",age:"age1"},
{id:"id2",name:"name2",age:"age2"},
{id:"id3",name:"name3",age:"age3"}
]
I want to create a JSON key value object from this array as follows.
json_object = {id1:name1, id2:name2, id3:name3}
input = [ {id:"id1",name:"name1",age:"age1"},
{id:"id2",name:"name2",age:"age2"},
{id:"id3",name:"name3",age:"age3"}]
require 'json'
JSON.dump(input.map { |hash| [hash[:id], hash[:name]] }.to_h)
#⇒ '{"id1":"name1","id2":"name2","id3":"name3"}'
.to_h like that on an array of arrays. Super nice! Would you please comment on JSON.dump vs. .to_json?to_json might be explicitly blocked/overwritten/whatever.
to_json in the ruby core. The thing is Rails or whoever do extensively overwrite/monkeypatch the default Ruby implementation, and what I need is an old good one from ruby core.Give this a go:
students = [
{id:"id1",name:"name1",age:"age1"},
{id:"id2",name:"name2",age:"age2"},
{id:"id3",name:"name3",age:"age3"}
]
json_object = students.each_with_object({}) do |hsh, returning|
returning[hsh[:id]] = hsh[:name]
end.to_json
In console:
puts json_object
=> {"id1":"name1","id2":"name2","id3":"name3"}
Your data is all identical, but if you wanted to generate a hash that took the value of students[n][:id] as keys and students[n][:name] as values you could do this:
student_ids_to_names = students.each_with_object({}) do |student, memo|
memo[student[:id]] = student[:name]
end
For your data, you'd end up with only one entry as the students are identical: { "id1" => "name1" }. If the data were different each key would be unique on :id.
Once you have a hash, you can call json_object = students_ids_to_names.to_json to get a JSON string.
each_with_object over inject for mutable accumulators.