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|
# frozen-string-literal: true
require 'csv'
module Sequel
module Plugins
# csv_serializer handles serializing entire Sequel::Model objects to CSV,
# as well as support for deserializing CSV directly into Sequel::Model
# objects. It requires the csv standard library.
#
# Basic Example:
#
# album = Album[1]
# album.to_csv(write_headers: true)
# # => "id,name,artist_id\n1,RF,2\n"
#
# You can provide options to control the CSV output:
#
# album.to_csv(only: :name)
# album.to_csv(except: [:id, :artist_id])
# # => "RF\n"
#
# +to_csv+ also exists as a class and dataset method, both of which return
# all objects in the dataset:
#
# Album.to_csv
# Album.where(artist_id: 1).to_csv
#
# If you have an existing array of model instances you want to convert to
# CSV, you can call the class to_csv method with the :array option:
#
# Album.to_csv(array: [Album[1], Album[2]])
#
# In addition to creating CSV, this plugin also enables Sequel::Model
# classes to create instances directly from CSV using the from_csv class
# method:
#
# csv = album.to_csv
# album = Album.from_csv(csv)
#
# The array_from_csv class method exists to parse arrays of model instances
# from CSV:
#
# csv = Album.where(artist_id: 1).to_csv
# albums = Album.array_from_csv(csv)
#
# These do not necessarily round trip, since doing so would let users
# create model objects with arbitrary values. By default, from_csv will
# call set with the values in the hash. If you want to specify the allowed
# fields, you can use the :headers option.
#
# Album.from_csv(album.to_csv, headers: %w'id name')
#
# If you want to update an existing instance, you can use the from_csv
# instance method:
#
# album.from_csv(csv)
#
# Usage:
#
# # Add CSV output capability to all model subclass instances (called
# # before loading subclasses)
# Sequel::Model.plugin :csv_serializer
#
# # Add CSV output capability to Album class instances
# Album.plugin :csv_serializer
module CsvSerializer
# Set up the column readers to do deserialization and the column writers
# to save the value in deserialized_values
def self.configure(model, opts = OPTS)
model.instance_exec do
@csv_serializer_opts = (@csv_serializer_opts || OPTS).merge(opts)
end
end
# Avoid keyword argument separation warnings on Ruby 2.7, while still
# being compatible with 1.9.
if RUBY_VERSION >= "2.0"
instance_eval(<<-END, __FILE__, __LINE__+1)
def self.csv_call(*args, opts, &block)
CSV.send(*args, **opts, &block)
end
END
else
# :nocov:
# :nodoc:
def self.csv_call(*args, opts, &block)
CSV.send(*args, opts, &block)
end
# :nodoc:
# :nocov:
end
module ClassMethods
# The default opts to use when serializing model objects to CSV
attr_reader :csv_serializer_opts
# Attempt to parse an array of instances from the given CSV string
def array_from_csv(csv, opts = OPTS)
CsvSerializer.csv_call(:parse, csv, process_csv_serializer_opts(opts)).map do |row|
row = row.to_hash
row.delete(nil)
new(row)
end
end
# Freeze csv serializier opts when freezing model class
def freeze
@csv_serializer_opts.freeze.each_value do |v|
v.freeze if v.is_a?(Array) || v.is_a?(Hash)
end
super
end
# Attempt to parse a single instance from the given CSV string
def from_csv(csv, opts = OPTS)
new.from_csv(csv, opts)
end
# Convert the options hash to one that can be passed to CSV.
def process_csv_serializer_opts(opts)
opts = (csv_serializer_opts || OPTS).merge(opts)
opts_cols = opts.delete(:columns)
opts_include = opts.delete(:include)
opts_except = opts.delete(:except)
only = opts.delete(:only)
opts[:headers] ||= Array(only || opts_cols || columns) + Array(opts_include) - Array(opts_except)
opts
end
Plugins.inherited_instance_variables(
self, :@csv_serializer_opts => lambda do |csv_serializer_opts|
opts = {}
csv_serializer_opts.each do |k, v|
opts[k] = (v.is_a?(Array) || v.is_a?(Hash)) ? v.dup : v
end
opts
end)
Plugins.def_dataset_methods(self, :to_csv)
end
module InstanceMethods
# Update the object using the data provided in the first line in CSV. Options:
#
# :headers :: The headers to use for the CSV line. Use nil for a header
# to specify the column should be ignored.
def from_csv(csv, opts = OPTS)
row = CsvSerializer.csv_call(:parse_line, csv, model.process_csv_serializer_opts(opts)).to_hash
row.delete(nil)
set(row)
end
# Return a string in CSV format. Accepts the same options as CSV.new,
# as well as the following options:
#
# :except :: Symbol or Array of Symbols of columns not to include in
# the CSV output.
# :only :: Symbol or Array of Symbols of columns to include in the CSV
# output, ignoring all other columns
# :include :: Symbol or Array of Symbols specifying non-column
# attributes to include in the CSV output.
def to_csv(opts = OPTS)
opts = model.process_csv_serializer_opts(opts)
headers = opts[:headers]
CsvSerializer.csv_call(:generate, model.process_csv_serializer_opts(opts)) do |csv|
csv << headers.map{|k| public_send(k)}
end
end
end
module DatasetMethods
# Return a CSV string representing an array of all objects in this
# dataset. Takes the same options as the instance method, and passes
# them to every instance. Accepts the same options as CSV.new, as well
# as the following options:
#
# :array :: An array of instances. If this is not provided, calls #all
# on the receiver to get the array.
def to_csv(opts = OPTS)
opts = model.process_csv_serializer_opts({:columns=>columns}.merge!(opts))
items = opts.delete(:array) || self
headers = opts[:headers]
CsvSerializer.csv_call(:generate, opts) do |csv|
items.each do |object|
csv << headers.map{|header| object.public_send(header)}
end
end
end
end
end
end
end
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