Class: FasterCSV

Class | FasterCSV
In: | lib/faster_csv.rb
Parent: | Object

This class provides a complete interface to CSV files and data. It offers tools to enable you to read and write to and from Strings or IO objects, as needed.

## Reading

### From a File

#### A Line at a Time

      FasterCSV.foreach("path/to/file.csv") do |row|
        # use row here...
      end

#### All at Once

      arr_of_arrs = FasterCSV.read("path/to/file.csv")

### From a String

#### A Line at a Time

      FasterCSV.parse("CSV,data,String") do |row|
        # use row here...
      end

#### All at Once

      arr_of_arrs = FasterCSV.parse("CSV,data,String")

## Writing

### To a File

      FasterCSV.open("path/to/file.csv", "w") do |csv|
        csv << ["row", "of", "CSV", "data"]
        csv << ["another", "row"]
        # ...
      end

### To a String

      csv_string = FasterCSV.generate do |csv|
        csv << ["row", "of", "CSV", "data"]
        csv << ["another", "row"]
        # ...
      end

## Convert a Single Line

      csv_string = ["CSV", "data"].to_csv   # to CSV
      csv_array  = "CSV,String".parse_csv   # from CSV

## Shortcut Interface

      FCSV             { |csv_out| csv_out << %w{my data here} }  # to $stdout
      FCSV(csv = "")   { |csv_str| csv_str << %w{my data here} }  # to a String
      FCSV($stderr)    { |csv_err| csv_err << %w{my data here} }  # to $stderr

### Methods

<< add_row build_csv_interface convert dump each filter foreach generate generate_line gets header_convert header_row? inspect instance load new open parse parse_line puts read read readline readlines readlines rewind shift table

### Included Modules

Enumerable

### Classes and Modules

Class FasterCSV::MalformedCSVError
Class FasterCSV::Row
Class FasterCSV::Table

### Constants

VERSION | = | "1.5.0".freeze |  | The version of the installed library.
FieldInfo | = | Struct.new(:index, :line, :header) |  | A FieldInfo Struct contains details about a field‘s position in the data source it was read from. FasterCSV will pass this Struct to some blocks that make decisions based on field structure. See FasterCSV.convert_fields() for an example.
`index`: | The zero-based index of the field in its row.
`line`: | The line of the data source this row is from.
`header`: | The header for the column, when available.
DateMatcher | = | / \A(?: (\w+,?\s+)?\w+\s+\d{1,2},?\s+\d{2,4} | \d{4}-\d{2}-\d{2} )\z /x |  | A Regexp used to find and convert some common Date formats.
DateTimeMatcher | = | / \A(?: (\w+,?\s+)?\w+\s+\d{1,2}\s+\d{1,2}:\d{1,2}:\d{1,2},?\s+\d{2,4} | \d{4}-\d{2}-\d{2}\s\d{2}:\d{2}:\d{2} )\z /x |  | A Regexp used to find and convert some common DateTime formats.
Converters | = | { :integer => lambda { |f| Integer(f) rescue f }, :float => lambda { |f| Float(f) rescue f }, :numeric => [:integer, :float], :date => lambda { |f| f =~ DateMatcher ? (Date.parse(f) rescue f) : f |  | This Hash holds the built-in converters of FasterCSV that can be accessed by name. You can select Converters with FasterCSV.convert() or through the `options` Hash passed to FasterCSV::new().
`:integer`: | Converts any field Integer() accepts.
`:float`: | Converts any field Float() accepts.
`:numeric`: | A combination of `:integer` and `:float`.
`:date`: | Converts any field Date::parse() accepts.
`:date_time`: | Converts any field DateTime::parse() accepts.
`:all`: | All built-in converters. A combination of `:date_time` and `:numeric`.
This Hash is intetionally left unfrozen and users should feel free to add values to it that can be accessed by all FasterCSV objects. To add a combo field, the value should be an Array of names. Combo fields can be nested with other combo fields.
HeaderConverters | = | { :downcase => lambda { |h| h.downcase }, :symbol => lambda { |h| h.downcase.tr(" ", "_").delete("^a-z0-9_").to_sym |  | This Hash holds the built-in header converters of FasterCSV that can be accessed by name. You can select HeaderConverters with FasterCSV.header_convert() or through the `options` Hash passed to FasterCSV::new().
`:downcase`: | Calls downcase() on the header String.
`:symbol`: | The header String is downcased, spaces are replaced with underscores, non-word characters are dropped, and finally to_sym() is called.
This Hash is intetionally left unfrozen and users should feel free to add values to it that can be accessed by all FasterCSV objects. To add a combo field, the value should be an Array of names. Combo fields can be nested with other combo fields.
DEFAULT_OPTIONS | = | { :col_sep => ",", :row_sep => :auto, :quote_char => '"', :converters => nil, :unconverted_fields => nil, :headers => false, :return_headers => false, :header_converters => nil, :skip_blanks => false, :force_quotes => false }.freeze |  | The options used when no overrides are given by calling code. They are:
`:col_sep`: | `","`
`:row_sep`: | `:auto`
`:quote_char`: | `’"’`
`:converters`: | `nil`
`:unconverted_fields`: | `nil`
`:headers`: | `false`
`:return_headers`: | `false`
`:header_converters`: | `nil`
`:skip_blanks`: | `false`
`:force_quotes`: | `false`

### Attributes

lineno | [R] | The line number of the last row read from this file. Fields with nested line-end characters will not affect this count.

### Public Class methods

build_csv_interface()

This method will build a drop-in replacement for many of the standard CSV methods. It allows you to write code like:

      begin
        require "faster_csv"
        FasterCSV.build_csv_interface
      rescue LoadError
        require "csv"
      end
      # ... use CSV here ...

This is not a complete interface with completely identical behavior. However, it is intended to be close enough that you won‘t notice the difference in most cases. CSV methods supported are:

- foreach()
- generate_line()
- open()
- parse()
- parse_line()
- readlines()

Be warned that this interface is slower than vanilla FasterCSV due to the extra layer of method calls. Depending on usage, this can slow it down to near CSV speeds.

dump(ary_of_objs, io = "", options = Hash.new)

This method allows you to serialize an Array of Ruby objects to a String or File of CSV data. This is not as powerful as Marshal or YAML, but perhaps useful for spreadsheet and database interaction.

Out of the box, this method is intended to work with simple data objects or Structs. It will serialize a list of instance variables and/or Struct.members().

If you need need more complicated serialization, you can control the process by adding methods to the class to be serialized.

A class method csv_meta() is responsible for returning the first row of the document (as an Array). This row is considered to be a Hash of the form key_1,value_1,key_2,value_2,… FasterCSV::load() expects to find a class key with a value of the stringified class name and FasterCSV::dump() will create this, if you do not define this method. This method is only called on the first object of the Array.

The next method you can provide is an instance method called csv_headers(). This method is expected to return the second line of the document (again as an Array), which is to be used to give each column a header. By default, FasterCSV::load() will set an instance variable if the field header starts with an @ character or call send() passing the header as the method name and the field value as an argument. This method is only called on the first object of the Array.

Finally, you can provide an instance method called csv_dump(), which will be passed the headers. This should return an Array of fields that can be serialized for this object. This method is called once for every object in the Array.

The `io` parameter can be used to serialize to a File, and `options` can be anything FasterCSV::new() accepts.

filter( options = Hash.new ) { |row| ... }
filter( input, options = Hash.new ) { |row| ... }
filter( input, output, options = Hash.new ) { |row| ... }

This method is a convenience for building Unix-like filters for CSV data. Each row is yielded to the provided block which can alter it as needed. After the block returns, the row is appended to `output` altered or not.

The `input` and `output` arguments can be anything FasterCSV::new() accepts (generally String or IO objects). If not given, they default to `ARGF` and `$stdout`.

The `options` parameter is also filtered down to FasterCSV::new() after some clever key parsing. Any key beginning with `:in_` or `:input_` will have that leading identifier stripped and will only be used in the `options` Hash for the `input` object. Keys starting with `:out_` or `:output_` affect only `output`. All other keys are assigned to both objects.

The `:output_row_sep` `option` defaults to `$INPUT_RECORD_SEPARATOR` (`$/`).

foreach(path, options = Hash.new, &block)

This method is intended as the primary interface for reading CSV files. You pass a `path` and any `options` you wish to set for the read. Each row of file will be passed to the provided `block` in turn.

The `options` parameter can be anything FasterCSV::new() understands.

generate( str, options = Hash.new ) { |faster_csv| ... }
generate( options = Hash.new ) { |faster_csv| ... }

This method wraps a String you provide, or an empty default String, in a FasterCSV object which is passed to the provided block. You can use the block to append CSV rows to the String and when the block exits, the final String will be returned.

Note that a passed String is modfied by this method. Call dup() before passing if you need a new String.

The `options` parameter can be anthing FasterCSV::new() understands.

generate_line(row, options = Hash.new)

This method is a shortcut for converting a single row (Array) into a CSV String.

The `options` parameter can be anthing FasterCSV::new() understands.

The `:row_sep` `option` defaults to `$INPUT_RECORD_SEPARATOR` (`$/`) when calling this method.

instance(data = $stdout, options = Hash.new) {|instance| ...}

This method will return a FasterCSV instance, just like FasterCSV::new(), but the instance will be cached and returned for all future calls to this method for the same `data` object (tested by Object#object_id()) with the same `options`.

If a block is given, the instance is passed to the block and the return value becomes the return value of the block.

load(io_or_str, options = Hash.new)

This method is the reading counterpart to FasterCSV::dump(). See that method for a detailed description of the process.

You can customize loading by adding a class method called csv_load() which will be passed a Hash of meta information, an Array of headers, and an Array of fields for the object the method is expected to return.

Remember that all fields will be Strings after this load. If you need something else, use `options` to setup converters or provide a custom csv_load() implementation.

new(data, options = Hash.new)

This constructor will wrap either a String or IO object passed in `data` for reading and/or writing. In addition to the FasterCSV instance methods, several IO methods are delegated. (See FasterCSV::open() for a complete list.) If you pass a String for `data`, you can later retrieve it (after writing to it, for example) with FasterCSV.string().

Note that a wrapped String will be positioned at at the beginning (for reading). If you want it at the end (for writing), use FasterCSV::generate(). If you want any other positioning, pass a preset StringIO object instead.

You may set any reading and/or writing preferences in the `options` Hash. Available options are:

`:col_sep`: | The String placed between each field.
`:row_sep`: | The String appended to the end of each row. This can be set to the special `:auto` setting, which requests that FasterCSV automatically discover this from the data. Auto-discovery reads ahead in the data looking for the next `"\r\n"`, `"\n"`, or `"\r"` sequence. A sequence will be selected even if it occurs in a quoted field, assuming that you would have the same line endings there. If none of those sequences is found, `data` is `ARGF`, `STDIN`, `STDOUT`, or `STDERR`, or the stream is only available for output, the default `$INPUT_RECORD_SEPARATOR` (`$/`) is used. Obviously, discovery takes a little time. Set manually if speed is important. Also note that IO objects should be opened in binary mode on Windows if this feature will be used as the line-ending translation can cause problems with resetting the document position to where it was before the read ahead.
`:quote_char`: | The character used to quote fields. This has to be a single character String. This is useful for application that incorrectly use `‘` as the quote character instead of the correct `"`. FasterCSV will always consider a double sequence this character to be an escaped quote.
`:encoding`: | The encoding to use when parsing the file. Defaults to your `$KDOCE` setting. Valid values: ``n’` or ``N’` for none, ``e’` or ``E’` for EUC, ``s’` or ``S’` for SJIS, and ``u’` or ``U’` for UTF-8 (see Regexp.new()).
`:field_size_limit`: | This is a maximum size FasterCSV will read ahead looking for the closing quote for a field. (In truth, it reads to the first line ending beyond this size.) If a quote cannot be found within the limit FasterCSV will raise a MalformedCSVError, assuming the data is faulty. You can use this limit to prevent what are effectively DoS attacks on the parser. However, this limit can cause a legitimate parse to fail and thus is set to `nil`, or off, by default.
`:converters`: | An Array of names from the Converters Hash and/or lambdas that handle custom conversion. A single converter doesn‘t have to be in an Array.
`:unconverted_fields`: | If set to `true`, an unconverted_fields() method will be added to all returned rows (Array or FasterCSV::Row) that will return the fields as they were before convertion. Note that `:headers` supplied by Array or String were not fields of the document and thus will have an empty Array attached.
`:headers`: | If set to `:first_row` or `true`, the initial row of the CSV file will be treated as a row of headers. If set to an Array, the contents will be used as the headers. If set to a String, the String is run through a call of FasterCSV::parse_line() with the same `:col_sep`, `:row_sep`, and `:quote_char` as this instance to produce an Array of headers. This setting causes FasterCSV.shift() to return rows as FasterCSV::Row objects instead of Arrays and FasterCSV.read() to return FasterCSV::Table objects instead of an Array of Arrays.
`:return_headers`: | When `false`, header rows are silently swallowed. If set to `true`, header rows are returned in a FasterCSV::Row object with identical headers and fields (save that the fields do not go through the converters).
`:write_headers`: | When `true` and `:headers` is set, a header row will be added to the output.
`:header_converters`: | Identical in functionality to `:converters` save that the conversions are only made to header rows.
`:skip_blanks`: | When set to a `true` value, FasterCSV will skip over any rows with no content.
`:force_quotes`: | When set to a `true` value, FasterCSV will quote all CSV fields it creates.

See FasterCSV::DEFAULT_OPTIONS for the default settings.

Options cannot be overriden in the instance methods for performance reasons, so be sure to set what you want here.

open( filename, mode="rb", options = Hash.new ) { |faster_csv| ... }
open( filename, mode="rb", options = Hash.new )

This method opens an IO object, and wraps that with FasterCSV. This is intended as the primary interface for writing a CSV file.

You may pass any `args` Ruby‘s open() understands followed by an optional Hash containing any `options` FasterCSV::new() understands.

This method works like Ruby‘s open() call, in that it will pass a FasterCSV object to a provided block and close it when the block termminates, or it will return the FasterCSV object when no block is provided. (Note: This is different from the standard CSV library which passes rows to the block. Use FasterCSV::foreach() for that behavior.)

An opened FasterCSV object will delegate to many IO methods, for convenience. You may call:

- binmode()
- close()
- close_read()
- close_write()
- closed?()
- eof()
- eof?()
- fcntl()
- fileno()
- flush()
- fsync()
- ioctl()
- isatty()
- pid()
- pos()
- reopen()
- seek()
- stat()
- sync()
- sync=()
- tell()
- to_i()
- to_io()
- tty?()

parse( str, options = Hash.new ) { |row| ... }
parse( str, options = Hash.new )

This method can be used to easily parse CSV out of a String. You may either provide a `block` which will be called with each row of the String in turn, or just use the returned Array of Arrays (when no `block` is given).

You pass your `str` to read from, and an optional `options` Hash containing anything FasterCSV::new() understands.

parse_line(line, options = Hash.new)

This method is a shortcut for converting a single line of a CSV String into a into an Array. Note that if `line` contains multiple rows, anything beyond the first row is ignored.

The `options` parameter can be anthing FasterCSV::new() understands.

read(path, options = Hash.new)

Use to slurp a CSV file into an Array of Arrays. Pass the `path` to the file and any `options` FasterCSV::new() understands.

readlines(*args)

Alias for FasterCSV::read().

table(path, options = Hash.new)

A shortcut for:

      FasterCSV.read( path, { :headers           => true,
                              :converters        => :numeric,
                              :header_converters => :symbol }.merge(options) )

### Public Instance methods

<<(row)

The primary write method for wrapped Strings and IOs, `row` (an Array or FasterCSV::Row) is converted to CSV and appended to the data source. When a FasterCSV::Row is passed, only the row‘s fields() are appended to the output.

The data source must be open for writing.

add_row(row)

Alias for #<<

convert( name )
convert { |field| ... }
convert { |field, field_info| ... }

You can use this method to install a FasterCSV::Converters built-in, or provide a block that handles a custom conversion.

If you provide a block that takes one argument, it will be passed the field and is expected to return the converted value or the field itself. If your block takes two arguments, it will also be passed a FieldInfo Struct, containing details about the field. Again, the block should return a converted field or the field itself.

each() {|row| ...}

Yields each row of the data source in turn.

Support for Enumerable.

The data source must be open for reading.

gets()

Alias for shift

header_convert( name )
header_convert { |field| ... }
header_convert { |field, field_info| ... }

Identical to FasterCSV.convert(), but for header rows.

Note that this method must be called before header rows are read to have any effect.

header_row?()

Returns `true` if the next row read will be a header row.

inspect()

Returns a simplified description of the key FasterCSV attributes.

puts(row)

Alias for #<<

read()

Slurps the remaining rows and returns an Array of Arrays.

The data source must be open for reading.

readline()

Alias for shift

readlines()

Alias for read

rewind()

Rewinds the underlying IO object and resets FasterCSV‘s lineno() counter.

shift()

The primary read method for wrapped Strings and IOs, a single row is pulled from the data source, parsed and returned as an Array of fields (if header rows are not used) or a FasterCSV::Row (when header rows are used).

The data source must be open for reading.

[Validate]