How to remove a row from a CSV with Ruby

问题:

Given the following CSV file, how would you remove all rows that contain the word 'true' in the column 'foo'?

Date,foo,bar
2014/10/31,true,derp
2014/10/31,false,derp

I have a working solution, however it requires making a secondary CSV object csv_no_foo

@csv = CSV.read(@csvfile, headers: true) #http://bit.ly/1mSlqfA
@headers = CSV.open(@csvfile,'r', :headers => true).read.headers

# Make a new CSV
@csv_no_foo = CSV.new(@headers)

@csv.each do |row|
  # puts row[5]
  if row[@headersHash['foo']] == 'false'
    @csv_no_foo.add_row(row)
  else
    puts "not pushing row #{row}"
  end
end

Ideally, I would just remove the offending row from the CSV like so:

...
 if row[@headersHash['foo']] == 'false'
    @csv.delete(true) #Doesn't work
...

Looking at the ruby documentation, it looks like the row class has a delete_if function. I'm confused on the syntax that that function requires. Is there a way to remove the row without making a new csv object?

http://ruby-doc.org/stdlib-1.9.2/libdoc/csv/rdoc/CSV/Row.html#method-i-each

回答1:

You should be able to use CSV::Table#delete_if, but you need to use CSV::table instead of CSV::read, because the former will give you a CSV::Table object, whereas the latter results in an Array of Arrays. Be aware that this setting will also convert the headers to symbols.

table = CSV.table(@csvfile)

table.delete_if do |row|
  row[:foo] == 'true'
end

File.open(@csvfile, 'w') do |f|
  f.write(table.to_csv)
end

回答2:

You might want to filter rows in a ruby manner:

require 'csv' 
csv = CSV.parse(File.read(@csvfile), {
  :col_sep => ",", 
  :headers => true
  }
).collect { |item| item[:foo] != 'true' }

Hope it help.