class CSV::Table

CSV::Table

A CSV::Table instance represents CSV data. (see class CSV).

The instance may have:

Instance Methods

CSV::Table has three groups of instance methods:

Creating a CSV::Table Instance

Commonly, a new CSV::Table instance is created by parsing CSV source using headers:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
table.class # => CSV::Table

You can also create an instance directly. See ::new.

Headers

If a table has headers, the headers serve as labels for the columns of data. Each header serves as the label for its column.

The headers for a CSV::Table object are stored as an Array of Strings.

Commonly, headers are defined in the first row of CSV source:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
table.headers # => ["Name", "Value"]

If no headers are defined, the Array is empty:

table = CSV::Table.new([])
table.headers # => []

Access Modes

CSV::Table provides three modes for accessing table data:

The access mode for aCSV::Table instance affects the behavior of some of its instance methods:

Row Mode

Set a table to row mode with method by_row!:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
table.by_row! # => #<CSV::Table mode:row row_count:4>

Specify a single row by an Integer index:

# Get a row.
table[1] # => #<CSV::Row "Name":"bar" "Value":"1">
# Set a row, then get it.
table[1] = CSV::Row.new(['Name', 'Value'], ['bam', 3])
table[1] # => #<CSV::Row "Name":"bam" "Value":3>

Specify a sequence of rows by a Range:

# Get rows.
table[1..2] # => [#<CSV::Row "Name":"bam" "Value":3>, #<CSV::Row "Name":"baz" "Value":"2">]
# Set rows, then get them.
table[1..2] = [
  CSV::Row.new(['Name', 'Value'], ['bat', 4]),
  CSV::Row.new(['Name', 'Value'], ['bad', 5]),
]
table[1..2] # => [["Name", #<CSV::Row "Name":"bat" "Value":4>], ["Value", #<CSV::Row "Name":"bad" "Value":5>]]

Column Mode

Set a table to column mode with method by_col!:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
table.by_col! # => #<CSV::Table mode:col row_count:4>

Specify a column by an Integer index:

# Get a column.
table[0]
# Set a column, then get it.
table[0] = ['FOO', 'BAR', 'BAZ']
table[0] # => ["FOO", "BAR", "BAZ"]

Specify a column by its String header:

# Get a column.
table['Name'] # => ["FOO", "BAR", "BAZ"]
# Set a column, then get it.
table['Name'] = ['Foo', 'Bar', 'Baz']
table['Name'] # => ["Foo", "Bar", "Baz"]

Mixed Mode

In mixed mode, you can refer to either rows or columns:

Set a table to mixed mode with method by_col_or_row!:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
table.by_col_or_row! # => #<CSV::Table mode:col_or_row row_count:4>

Specify a single row by an Integer index:

# Get a row.
table[1] # => #<CSV::Row "Name":"bar" "Value":"1">
# Set a row, then get it.
table[1] = CSV::Row.new(['Name', 'Value'], ['bam', 3])
table[1] # => #<CSV::Row "Name":"bam" "Value":3>

Specify a sequence of rows by a Range:

# Get rows.
table[1..2] # => [#<CSV::Row "Name":"bam" "Value":3>, #<CSV::Row "Name":"baz" "Value":"2">]
# Set rows, then get them.
table[1] = CSV::Row.new(['Name', 'Value'], ['bat', 4])
table[2] = CSV::Row.new(['Name', 'Value'], ['bad', 5])
table[1..2] # => [["Name", #<CSV::Row "Name":"bat" "Value":4>], ["Value", #<CSV::Row "Name":"bad" "Value":5>]]

Specify a column by its String header:

# Get a column.
table['Name'] # => ["foo", "bat", "bad"]
# Set a column, then get it.
table['Name'] = ['Foo', 'Bar', 'Baz']
table['Name'] # => ["Foo", "Bar", "Baz"]