Class: FasterCSV::Table

Inherits:
Object
  • Object
show all
Extended by:
Forwardable
Includes:
Enumerable
Defined in:
lib/faster_csv.rb

Overview

A FasterCSV::Table is a two-dimensional data structure for representing CSV documents. Tables allow you to work with the data by row or column, manipulate the data, and even convert the results back to CSV, if needed.

All tables returned by FasterCSV will be constructed from this class, if header row processing is activated.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(array_of_rows) ⇒ Table

Construct a new FasterCSV::Table from array_of_rows, which are expected to be FasterCSV::Row objects. All rows are assumed to have the same headers.

A FasterCSV::Table object supports the following Array methods through delegation:

  • empty?()

  • length()

  • size()



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# File 'lib/faster_csv.rb', line 426

def initialize(array_of_rows)
  @table = array_of_rows
  @mode  = :col_or_row
end

Instance Attribute Details

#mode ⇒ Object (readonly)

The current access mode for indexing and iteration.



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# File 'lib/faster_csv.rb', line 432

def mode
  @mode
end

Instance Method Details

#<<(row_or_array) ⇒ Object

Adds a new row to the bottom end of this table. You can provide an Array, which will be converted to a FasterCSV::Row (inheriting the table’s headers()), or a FasterCSV::Row.

This method returns the table for chaining.



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# File 'lib/faster_csv.rb', line 624

def <<(row_or_array)
  if row_or_array.is_a? Array  # append Array
    @table << Row.new(headers, row_or_array)
  else                         # append Row
    @table << row_or_array
  end

  self  # for chaining
end

#==(other) ⇒ Object

Returns true if all rows of this table ==() other‘s rows.



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# File 'lib/faster_csv.rb', line 703

def ==(other)
  @table == other.table
end

#[](index_or_header) ⇒ Object

In the default mixed mode, this method returns rows for index access and columns for header access. You can force the index association by first calling by_col!() or by_row!().

Columns are returned as an Array of values. Altering that Array has no effect on the table.



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# File 'lib/faster_csv.rb', line 540

def [](index_or_header)
  if @mode == :row or  # by index
     (@mode == :col_or_row and index_or_header.is_a? Integer)
    @table[index_or_header]
  else                 # by header
    @table.map { |row| row[index_or_header] }
  end
end

#[]=(index_or_header, value) ⇒ Object

In the default mixed mode, this method assigns rows for index access and columns for header access. You can force the index association by first calling by_col!() or by_row!().

Rows may be set to an Array of values (which will inherit the table’s headers()) or a FasterCSV::Row.

Columns may be set to a single value, which is copied to each row of the column, or an Array of values. Arrays of values are assigned to rows top to bottom in row major order. Excess values are ignored and if the Array does not have a value for each row the extra rows will receive a nil.

Assigning to an existing column or row clobbers the data. Assigning to new columns creates them at the right end of the table.



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# File 'lib/faster_csv.rb', line 565

def []=(index_or_header, value)
  if @mode == :row or  # by index
     (@mode == :col_or_row and index_or_header.is_a? Integer)
    if value.is_a? Array
      @table[index_or_header] = Row.new(headers, value)
    else
      @table[index_or_header] = value
    end
  else                 # set column
    if value.is_a? Array  # multiple values
      @table.each_with_index do |row, i|
        if row.header_row?
          row[index_or_header] = index_or_header
        else
          row[index_or_header] = value[i]
        end
      end
    else                  # repeated value
      @table.each do |row|
        if row.header_row?
          row[index_or_header] = index_or_header
        else
          row[index_or_header] = value
        end
      end
    end
  end
end

#by_col ⇒ Object

Returns a duplicate table object, in column mode. This is handy for chaining in a single call without changing the table mode, but be aware that this method can consume a fair amount of memory for bigger data sets.

This method returns the duplicate table for chaining. Don’t chain destructive methods (like []=()) this way though, since you are working with a duplicate.



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# File 'lib/faster_csv.rb', line 452

def by_col
  self.class.new(@table.dup).by_col!
end

#by_col! ⇒ Object

Switches the mode of this table to column mode. All calls to indexing and iteration methods will work with columns until the mode is changed again.

This method returns the table and is safe to chain.



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# File 'lib/faster_csv.rb', line 462

def by_col!
  @mode = :col

  self
end

#by_col_or_row ⇒ Object

Returns a duplicate table object, in mixed mode. This is handy for chaining in a single call without changing the table mode, but be aware that this method can consume a fair amount of memory for bigger data sets.

This method returns the duplicate table for chaining. Don’t chain destructive methods (like []=()) this way though, since you are working with a duplicate.



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# File 'lib/faster_csv.rb', line 477

def by_col_or_row
  self.class.new(@table.dup).by_col_or_row!
end

#by_col_or_row! ⇒ Object

Switches the mode of this table to mixed mode. All calls to indexing and iteration methods will use the default intelligent indexing system until the mode is changed again. In mixed mode an index is assumed to be a row reference while anything else is assumed to be column access by headers.

This method returns the table and is safe to chain.



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# File 'lib/faster_csv.rb', line 489

def by_col_or_row!
  @mode = :col_or_row

  self
end

#by_row ⇒ Object

Returns a duplicate table object, in row mode. This is handy for chaining in a single call without changing the table mode, but be aware that this method can consume a fair amount of memory for bigger data sets.

This method returns the duplicate table for chaining. Don’t chain destructive methods (like []=()) this way though, since you are working with a duplicate.



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# File 'lib/faster_csv.rb', line 504

def by_row
  self.class.new(@table.dup).by_row!
end

#by_row! ⇒ Object

Switches the mode of this table to row mode. All calls to indexing and iteration methods will work with rows until the mode is changed again.

This method returns the table and is safe to chain.



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# File 'lib/faster_csv.rb', line 514

def by_row!
  @mode = :row

  self
end

#delete(index_or_header) ⇒ Object

Removes and returns the indicated column or row. In the default mixed mode indices refer to rows and everything else is assumed to be a column header. Use by_col!() or by_row!() to force the lookup.



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# File 'lib/faster_csv.rb', line 652

def delete(index_or_header)
  if @mode == :row or  # by index
     (@mode == :col_or_row and index_or_header.is_a? Integer)
    @table.delete_at(index_or_header)
  else                 # by header
    @table.map { |row| row.delete(index_or_header).last }
  end
end

#delete_if(&block) ⇒ Object

Removes any column or row for which the block returns true. In the default mixed mode or row mode, iteration is the standard row major walking of rows. In column mode, interation will yield two element tuples containing the column name and an Array of values for that column.

This method returns the table for chaining.



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# File 'lib/faster_csv.rb', line 669

def delete_if(&block)
  if @mode == :row or @mode == :col_or_row  # by index
    @table.delete_if(&block)
  else                                      # by header
    to_delete = Array.new
    headers.each_with_index do |header, i|
      to_delete << header if block[[header, self[header]]]
    end
    to_delete.map { |header| delete(header) }
  end

  self  # for chaining
end

#each(&block) ⇒ Object

In the default mixed mode or row mode, iteration is the standard row major walking of rows. In column mode, interation will yield two element tuples containing the column name and an Array of values for that column.

This method returns the table for chaining.



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# File 'lib/faster_csv.rb', line 692

def each(&block)
  if @mode == :col
    headers.each { |header| block[[header, self[header]]] }
  else
    @table.each(&block)
  end

  self  # for chaining
end

#headers ⇒ Object

Returns the headers for the first row of this table (assumed to match all other rows). An empty Array is returned for empty tables.



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# File 'lib/faster_csv.rb', line 524

def headers
  if @table.empty?
    Array.new
  else
    @table.first.headers
  end
end

#inspect ⇒ Object 



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# File 'lib/faster_csv.rb', line 740

def inspect
  "#<#{self.class} mode:#{@mode} row_count:#{to_a.size}>"
end

#push(*rows) ⇒ Object

A shortcut for appending multiple rows. Equivalent to:

rows.each { |row| self << row }

This method returns the table for chaining.



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# File 'lib/faster_csv.rb', line 641

def push(*rows)
  rows.each { |row| self << row }

  self  # for chaining
end

#to_a ⇒ Object

Returns the table as an Array of Arrays. Headers will be the first row, then all of the field rows will follow.



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# File 'lib/faster_csv.rb', line 711

def to_a
  @table.inject([headers]) do |array, row|
    if row.header_row?
      array
    else
      array + [row.fields]
    end
  end
end

#to_csv(options = Hash.new) ⇒ Object Also known as: to_s

Returns the table as a complete CSV String. Headers will be listed first, then all of the field rows.

This method assumes you want the Table.headers(), unless you explicitly pass :write_headers => false.



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# File 'lib/faster_csv.rb', line 728

def to_csv(options = Hash.new)
  wh = options.fetch(:write_headers, true)
  @table.inject(wh ? [headers.to_csv(options)] : [ ]) do |rows, row|
    if row.header_row?
      rows
    else
      rows + [row.fields.to_csv(options)]
    end
  end.join
end

#values_at(*indices_or_headers) ⇒ Object

The mixed mode default is to treat a list of indices as row access, returning the rows indicated. Anything else is considered columnar access. For columnar access, the return set has an Array for each row with the values indicated by the headers in each Array. You can force column or row mode using by_col!() or by_row!().

You cannot mix column and row access.



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# File 'lib/faster_csv.rb', line 603

def values_at(*indices_or_headers)
  if @mode == :row or  # by indices
     ( @mode == :col_or_row and indices_or_headers.all? do |index|
                                  index.is_a?(Integer)         or
                                  ( index.is_a?(Range)         and
                                    index.first.is_a?(Integer) and
                                    index.last.is_a?(Integer) )
                                end )
    @table.values_at(*indices_or_headers)
  else                 # by headers
    @table.map { |row| row.values_at(*indices_or_headers) }
  end
end