value_converters.md

Contents

• Introduction
• The Basic Read API
• The Basic Write API
• Batch Processing
• Configuration Options
• Row and Column Separators
• Header Transformations
• Header Validations
• Data Transformations
• Value Converters

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Using Value Converters for Reading CSV

Value Converters allow you to do custom transformations specific rows, to help you massage the data so it fits the expectations of your down-stream process, such as creating a DB record.

If you use key_mappings and value_converters, make sure that the value converters references the keys based on the final mapped name, not the original name in the CSV file.

    $ cat spec/fixtures/with_dates.csv
    first,last,date,price,member
    Ben,Miller,10/30/1998,$44.50,TRUE
    Tom,Turner,2/1/2011,$15.99,False
    Ken,Smith,01/09/2013,$199.99,true

    $ irb
    > require 'smarter_csv'
    > require 'date'

    # define a custom converter class, which implements self.convert(value)
    class DateConverter
      def self.convert(value)
        Date.strptime( value, '%m/%d/%Y') # parses custom date format into Date instance
      end
    end

    class DollarConverter
      def self.convert(value)
        value.sub('$','').to_f # strips the dollar sign and creates a Float value
      end
    end

    require 'money'
    class MoneyConverter
      def self.convert(value)
        # depending on locale you might want to also remove the indicator for thousands, e.g. comma 
        Money.from_amount(value.gsub(/[\s\$]/,'').to_f) # creates a Money instance (based on cents)
      end
    end

    class BooleanConverter
      def self.convert(value)
        case value
        when /true/i
          true
        when /false/i
          false
        else
          nil
        end
      end
    end

    options = {value_converters: {date: DateConverter, price: DollarConverter, member: BooleanConverter}}
    data = SmarterCSV.process("spec/fixtures/with_dates.csv", options)
    first_record = data.first
    first_record[:date]
      => #<Date: 1998-10-30 ((2451117j,0s,0n),+0s,2299161j)>
    first_record[:date].class
      => Date
    first_record[:price]
      => 44.50
    first_record[:price].class
      => Float
    first_record[:member]
      => true

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