将数据解析为新行上的csv文件 - ruby

Question

I am trying to export data that I 'get' into a new csv file. Currently, my code below posts everyone onto a single line until it fills up and then it continues to the next line. I would like to have it where when data is imported, it starts on the following line below, creating a list of transactions.

def export_data
    File.open('coffee_orders.csv', 'a+') do |csv|
      puts @item_quantity = [Time.now, @item_name, @amount]
      csv << @item_quantity
    end
end

Answer 1

Basing it on your starting code, I'd do something like:

def export_data
  File.open('coffee_orders.csv', 'a') do |csv|
    csv << [Time.now, @item_name, @amount].join(', ')
  end
end

Or:

def export_data
  File.open('coffee_orders.csv', 'a') do |csv|
    csv << '%s, %s, %s' % [Time.now, @item_name, @amount].map(&:to_s)
  end
end

Notice, it's not necessary to use 'a+' to append to a file. Instead use 'a' only unless you absolutely need "read" mode while the file is open also. Here's what the IO.new documentation says:

"a"  Write-only, starts at end of file if file exists,
     otherwise creates a new file for writing.

"a+" Read-write, starts at end of file if file exists,
     otherwise creates a new file for reading and
     writing.

The way I'd write it for myself would be something like:

CSV_FILENAME = 'coffee_orders.csv'
def export_data
  csv_has_content = File.size?(CSV_FILENAME)
  CSV.open(CSV_FILENAME, 'a') do |csv|
    csv << %w[Time Item Amount] unless csv_has_content
    csv << [Time.now, @item_name, @amount]
  end
end

This uses Ruby's CSV class to handle all the ins-and-outs. It checks to see if the file already exists, and if it has no content it writes the header before writing the content.

Answer 2

Try this. It will add a new line after each transaction. When you append to it next, it will be from a new line.

def export_data
  File.open('coffee_orders.csv', 'a+') do |csv|
    csv.puts @item_quantity = [Time.now, @item_name, @amount]
  end
end

Although by looking the extension, you would probably want to confine it to csv format.

def export_data
  File.open('coffee_orders.csv', 'a+') do |csv|
    @item_quantity = [Time.now, @item_name, @amount]
    csv.puts @item_quantity.join(',')
  end
end