Writing to database row based on column name with FasterCSV

ruby-talk
1

Hello all,
I've added a couple new columns to a database table. I was trying to
add default data as the .csv file is being read into the table. I'm not
sure on how to do this.

- import_irb_file -
def import_irb_file
# set file name
  file = params[:irb][:file]
  deletecount = 0
  rowcount = 0

# delete all irb records
   @irb = Irb.find(:all, :conditions => "reconciled = 1")
   @irb.each { |i|
     i.destroy
     deletecount+=1
   }

   Irb.transaction do
   FasterCSV.parse(file,
                   :headers => true,
                   :header_converters => lambda { |h| h.tr(" ",
"_").delete("^a-zA-Z0-9_")},
                   :converters => :all ) do |row|
                   Irb.create!(row.to_hash)
                   rowcount += 1
            end
      end
      # if successful then display, then redirect to index page
      flash[:notice] = "Successfully deleted #{deletecount} and added
#{rowcount} IRB record(s)."
      redirect_to :action => :index

    rescue => exception
      file_name = params[:irb]['file'].original_filename
      file_parts = params[:irb]['file'].original_filename.split('.')
      ext = file_parts[1]

      if ext != 'csv'
        error = "CSV file is required"
      else
        error = ERB::Util.h(exception.to_s) # get the error and HTML
escape it
      end
      # If an exception in thrown, the transaction rolls back and we end
up in this
      # rescue block

      flash[:error] = "Error adding projects to IRB table. (#{error}).
Please try again."

      redirect_to :controller => 'irbs', :action => 'new'

  end

Thank you for any and all help with this.

JohnM

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2

I'm happy to try and help, but I'm not sure I understand the question. What are you trying to do?

James Edward Gray II

···

On Feb 2, 2010, at 1:22 PM, John Mcleod wrote:

I've added a couple new columns to a database table. I was trying to
add default data as the .csv file is being read into the table. I'm not
sure on how to do this.

Thank you for any and all help with this.

3

Thanks James for the reply.

I need to add default values (0) to 2 columns that are not in the csv.

For example,

        Column 1, Column 2, New Column 1, New Column 2
        --------- --------- ------------- ------------
Row 1 csv value csv value 0 0

When I go to create a row, I want to check for these column headers and
write to the table with a zero.

I'm not sure if it's easier to write to the csv first, adding the
columns, then parsing to the database or just do it all at once.

John

···

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4

How about changing this code:

  Irb.create!(row.to_hash)

to:

  Irb.create!( { "New Column 1" => 0,
                 "New Column 2" => 0 }.merge(row.to_hash) )

Does that do what you wanted?

James Edward Gray II

···

On Feb 2, 2010, at 1:42 PM, John Mcleod wrote:

I need to add default values (0) to 2 columns that are not in the csv.

For example,

       Column 1, Column 2, New Column 1, New Column 2
       --------- --------- ------------- ------------
Row 1 csv value csv value 0 0

When I go to create a row, I want to check for these column headers and
write to the table with a zero.

5

Yes,
Thank you James for your expertise.

Just a question to understand.

Using the .merge method, does this do the actual insert of the new
column data? or does it take the data and "merge" it into the csv before
the insert?
Is this in Ruby? I noticed it's not in the FasterCSV docs.

  Irb.create!( { "New Column 1" => 0,
                 "New Column 2" => 0 }.merge(row.to_hash) )

Thanks again.

John

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6

merge() is just Hash#merge() from Ruby, yes. It doesn't change the file, no. It just changes the data read before it is handed off to ActiveRecord.

James Edward Gray II

···

On Feb 2, 2010, at 2:19 PM, John Mcleod wrote:

Using the .merge method, does this do the actual insert of the new
column data? or does it take the data and "merge" it into the csv before
the insert?
Is this in Ruby? I noticed it's not in the FasterCSV docs.

7

Well, if I'd do a little detective work, I'd notice that I'm working
with Hashes. Therefore, the "Hash" class.

John

···

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