Rails：如果 Json 中有不同的属性，如何在 csv 文件中添加数据头？

Question

I have a array of data which is

user: [
   {name: 'foo', email: 'foo@gmail.com'},
   {name: 'foo', email: 'foo@gmail.com', phone: '76767676'},
   {name: 'foo', email: 'foo@gmail.com', pin_code: '22526'},
]

and I am changing it into csv by this code

CSV.open(file, 'w') do |csv|
  user_hash = JSON.parse(user.to_json)
  csv << user_hash.first.keys
  user_hash.each do |hash|
    csv << hash.values
  end
end 

in above code there is a problem that i am taking user_hash.first.keys so first keys name and email will be there for header.

I want to know that how can we add new column in header if a new attribute arrives which is happening in other two.

because I am taking the user_hash.first.keys so name and email header columns will be there not phone and pin_code.

Thanks.

Answer 1

You will need to collect all available keys first and then get the values for those keys in the same order for each hash.

user_hash = JSON.parse(user.to_json)
keys = user_hash.flat_map(&:keys).uniq

CSV.open(file, 'w') do |csv|
  csv << keys
  user_hash.each { |hash| csv << hash.values_at(*keys) }
end