Class: JobIteration::CsvEnumerator

Inherits:
Object
  • Object
show all
Defined in:
lib/job-iteration/csv_enumerator.rb

Overview

CsvEnumerator makes it possible to write an Iteration job that uses CSV file as a collection to Iterate.

Examples:

def build_enumerator(cursor:)
  csv = CSV.open('tmp/files', { converters: :integer, headers: true })
  JobIteration::CsvEnumerator.new(csv).rows(cursor: cursor)
end

def each_iteration(row)
  ...
end

Instance Method Summary collapse

Constructor Details

#initialize(csv) ⇒ JobIteration::CsvEnumerator

Constructs CsvEnumerator instance based on a CSV file.

Examples:

csv = CSV.open('tmp/files', { converters: :integer, headers: true })
JobIteration::CsvEnumerator.new(csv).rows(cursor: cursor)

Parameters:

  • csv (CSV)

    An instance of CSV object


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# File 'lib/job-iteration/csv_enumerator.rb', line 22

def initialize(csv)
  unless csv.instance_of?(CSV)
    raise ArgumentError, "CsvEnumerator.new takes CSV object"
  end

  @csv = csv
end

Instance Method Details

#batches(batch_size:, cursor:) ⇒ Enumerator

Constructs a enumerator on batches of CSV rows

Returns:

  • (Enumerator)

    Enumerator instance


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# File 'lib/job-iteration/csv_enumerator.rb', line 41

def batches(batch_size:, cursor:)
  @csv.lazy
    .each_slice(batch_size)
    .each_with_index
    .drop(cursor.to_i)
    .to_enum { (count_rows_in_file.to_f / batch_size).ceil }
end

#rows(cursor:) ⇒ Enumerator

Constructs a enumerator on CSV rows

Returns:

  • (Enumerator)

    Enumerator instance


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# File 'lib/job-iteration/csv_enumerator.rb', line 32

def rows(cursor:)
  @csv.lazy
    .each_with_index
    .drop(cursor.to_i)
    .to_enum { count_rows_in_file }
end