CsvRowModel

Import and export your custom CSVs with a intuitive shared Ruby interface.

First define your schema:

class ProjectRowModel
  include CsvRowModel::Model

  column :id
  column :name
end

To export, define your export model like ActiveModel::Serializer and generate the file:

class ProjectExportRowModel < ProjectRowModel
  include CsvRowModel::Export

  # this is an override with the default implementation
  def id
    source_model.id
  end
end

export_file = CsvRowModel::Export::File.new(ProjectExportRowModel)
export_file.generate { |csv| csv << project }
export_file.file # => <Tempfile>
export_file.to_s # => export_file.file.read

To import, define your import model, which works like ActiveRecord, and iterate through a file:

class ProjectImportRowModel < ProjectRowModel
  include CsvRowModel::Import

  # this is an override with the default implementation
  def id
    original_attribute(:id)
  end
end

import_file = CsvRowModel::Import::File.new(file_path, ProjectImportRowModel)
row_model = import_file.next

row_model.header # => ["id", "name"]

row_model.source_row # => ["1", "Some Project Name"]
row_model.mapped_row # => { id: "1", name: "Some Project Name" }, this is `source_row` mapped to `column_names`
row_model.attributes # => { id: "1", name: "Some Project Name" }, this is final attribute values mapped to `column_names`

row_model.id # => 1
row_model.name # => "Some Project Name"

row_model.previous # => <ProjectImportRowModel instance>
row_model.previous.previous # => nil, save memory by avoiding a linked list

Installation

Add this line to your application's Gemfile:

gem 'csv_row_model'

And then execute:

$ bundle

Or install it yourself as:

$ gem install csv_row_model

Export

Header Value

To generate a header value, the following pseudocode is executed:

def header(column_name)
  # 1. Header Option
  header = options(column_name)[:header]

  # 2. format_header
  header || format_header(column_name)
end

Header Option

Specify the header manually:

class ProjectRowModel
  include CsvRowModel::Model
  column :name, header: "NAME"
end

Format Header

Override the format_header method to format column header names:

class ProjectExportRowModel < ProjectRowModel
  include CsvRowModel::Export
  class << self
    def format_header(column_name)
      column_name.to_s.titleize
    end
  end
end

Import

Attribute Values

To generate a attribute value, the following pseudocode is executed:

def original_attribute(column_name)
  # 1. Get the raw CSV string value for the column
  value = mapped_row[column_name]

  # 2. Clean or format each cell
  value = self.class.format_cell(cell, column_name, column_index, context)

  if value.present?
    # 3a. Parse the cell value (which does nothing if no parsing is specified)
    parse(value)
  elsif default_exists?
    # 3b. Set the default
    default_for_column(column_name)
  end
end

def original_attributes; @original_attributes ||= { id: original_attribute(:id) } end

def id; original_attribute[:id] end

Format Cell

Override the format_cell method to clean/format every cell:

class ProjectImportRowModel < ProjectRowModel
  include CsvRowModel::Import
  class << self
    def format_cell(cell, column_name, column_index, context={})
      cell = cell.strip
      cell.blank? ? nil : cell
    end
  end
end

Type

Automatic type parsing.

class ProjectImportRowModel
  include CsvRowModel::Model
  include CsvRowModel::Import

  column :id, type: Integer
  column :name, parse: ->(original_string) { parse(original_string) }

  def parse(original_string)
    "#{id} - #{original_string}"
  end
end

There are validators for different types: Boolean, Date, Float, Integer. See Validations for more.

Default

Sets the default value of the cell:

class ProjectImportRowModel
  include CsvRowModel::Model
  include CsvRowModel::Import

  column :id, default: 1
  column :name, default: -> { get_name }

  def get_name; "John Doe" end
end
row_model = ProjectImportRowModel.new(["", ""])
row_model.id # => 1
row_model.name # => "John Doe"
row_model.default_changes # => { id: ["", 1], name: ["", "John Doe"] }

DefaultChangeValidator is provided to allows to add warnings when defaults are set. See Validations for more.

Advanced Import

Children

Child RowModel relationships can also be defined:

class UserImportRowModel
  include CsvRowModel::Model
  include CsvRowModel::Import

  column :id, type: Integer
  column :name
  column :email

  # uses ProjectImportRowModel#valid? to detect the child row
  has_many :projects, ProjectImportRowModel
end

import_file = CsvRowModel::Import::File.new(file_path, UserImportRowModel)
row_model = import_file.next
row_model.projects # => [<ProjectImportRowModel>, ...]

Layers

For complex RowModels there are different layers you can work with:

import_file = CsvRowModel::Import::File.new(file_path, ProjectImportRowModel)
row_model = import_file.next

# the three layers:
# 1. csv_string_model - represents the row BEFORE parsing (attributes are always strings)
row_model.csv_string_model

# 2. RowModel - represents the row AFTER parsing
row_model

# 3. Presenter - an abstraction of a row
row_model.presenter

CsvStringModel

The CsvStringModel represents a row before parsing to add parsing validations.

class ProjectImportRowModel
  include CsvRowModel::Model
  include CsvRowModel::Import

  # Note the type definition here for parsing
  column :id, type: Integer

  # this is applied to the parsed CSV on the model
  validates :id, numericality: { greater_than: 0 }

  csv_string_model do
    # define your csv_string_model here

    # this is applied BEFORE the parsed CSV on csv_string_model
    validates :id, presense: true

    def random_method; "Hihi" end
  end
end

# Applied to the String
ProjectImportRowModel.new([""])
csv_string_model = row_model.csv_string_model
csv_string_model.random_method => "Hihi"
csv_string_model.valid? => false
csv_string_model.errors.full_messages # => ["Id can't be blank'"]

# Errors are propagated for simplicity
row_model.valid? # => false
row_model.errors.full_messages # => ["Id can't be blank'"]

# Applied to the parsed Integer
row_model = ProjectRowModel.new(["-1"])
row_model.valid? # => false
row_model.errors.full_messages # => ["Id must be greater than 0"]

Note that CsvStringModel validations are calculated after Format Cell.

Presenter

For complex rows, you can wrap your RowModel with a presenter:

class ProjectImportRowModel < ProjectRowModel
  include CsvRowModel::Import

  presenter do
    # define your presenter here

    # this is shorthand for the psuedo_code:
    # def project
    #  return if row_model.id.blank? || row_model.name.blank?
    #
    #  # turn off memoziation with `memoize: false` option
    #  @project ||= __the_code_inside_the_block__
    # end
    #
    # and the psuedo_code:
    # def valid?
    #   super # calls ActiveModel::Errors code
    #   errors.delete(:project) if row_model.id.invalid? || row_model.name.invalid?
    #   errors.empty?
    # end
    attribute :project, dependencies: [:id, :name] do
      project = Project.where(id: row_model.id).first

      # project not found, invalid.
      return unless project

      project.name = row_model.name
      project
    end
  end
end

# Importing is the same
import_file = CsvRowModel::Import::File.new(file_path, ProjectImportRowModel)
row_model = import_file.next
presenter = row_model.presenter

presenter.row_model # gets the row model underneath
presenter.project.name == presenter.row_model.name # => "Some Project Name"

The presenters are designed for another layer of validation---such as with the database.

Also, the attribute defines a dynamic #project method that:

1. Memoizes by default, turn off with memoize: false option
2. All errors of row_model are propagated to the presenter when calling presenter.valid?
3. Handles dependencies:
   • When any of the dependencies are blank?, the attribute block is not called and the attribute returns nil.
   • When any of the dependencies are invalid?, presenter.errors for dependencies are cleaned. For the example above, if row_model.id/name are invalid?, then the :project key is removed from the errors, so: presenter.errors.keys # => [:id, :name]

Import Validations

Use ActiveModel::Validations the RowModel's Layers. Please read Layers for more information.

Included is ActiveWarnings on Model and Presenter for warnings.

Type Format

Notice that there are validators given for different types: Boolean, Date, Float, Integer:

class ProjectImportRowModel
  include CsvRowModel::Model
  include CsvRowModel::Import

  column :id, type: Integer, validate_type: true

  # the :validate_type option is the same as:
  # csv_string_model do
  #   validates :id, integer_format: true, allow_blank: true
  # end
end

ProjectRowModel.new(["not_a_number"])
row_model.valid? # => false
row_model.errors.full_messages # => ["Id is not a Integer format"]

Default Changes

Default Changes are tracked within ActiveWarnings.

class ProjectImportRowModel
  include CsvRowModel::Model
  include CsvRowModel::Input

  column :id, default: 1

  warnings do
    validates :id, default_change: true
  end
end

row_model = ProjectImportRowModel.new([""])

row_model.unsafe? # => true
row_model.has_warnings? # => true, same as `#unsafe?`
row_model.warnings.full_messages # => ["Id changed by default"]
row_model.default_changes # => { id: ["", 1] }

Skip and Abort

You can iterate through a file with the #each method, which calls #next internally. #next will always return the next RowModel in the file. However, you can implement skips and abort logic:

class ProjectImportRowModel
  # always skip
  def skip?
    true # original implementation: !valid? || presenter.skip?
  end
end

CsvRowModel::Import::File.new(file_path, ProjectImportRowModel).each do |project_import_model|
  # never yields here
end

Import Callbacks

CsvRowModel::Import::File can be subclassed to access ActiveModel::Callbacks.

• each_iteration - before, around, or after the an iteration on #each. Use this to handle exceptions. return and break may be called within the callback for skips and aborts.
• next - before, around, or after each change in current_row_model
• skip - before
• abort - before

and implement the callbacks:

class ImportFile < CsvRowModel::Import::File
  around_each_iteration :logger_track
  before_skip :track_skip

  def logger_track(&block)
    ...
  end

  def track_skip
    ...
  end
end

Dynamic columns

Dynamic columns are columns that can expand to many columns. Currently, we can only one dynamic column after all other standard columns. The following:

class DynamicColumnModel
  include CsvRowModel::Model

  column :first_name
  column :last_name
  # header is optional, below is the default_implementation
  dynamic_column :skills, header: ->(skill_name) { skill_name }
end

represents this table:

first_name	last_name	skill1	skill2
John	Doe	No	Yes
Mario	Super	Yes	No
Mike	Jackson	Yes	Yes

Export

Dynamic column attributes are arrays, but each item in the array is defined via singular attribute method like normal columns:

class DynamicColumnExportModel < DynamicColumnModel
  include CsvRowModel::Export

  def skill(skill_name)
    # below is an override, this is the default implementation: skill_name # => "skill1", then "skill2"
    source_model.skills.include?(skill_name) ? "Yes" : "No"
  end
end

# the `skills` context is mapped to generate an array
export_file = CsvRowModel::Export::File.new(DynamicColumnExportModel, { skills: Skill.all  })
export_file.generate do |csv|
  User.all.each { |user| csv << user }
end

Import

Like Export above, each item of the array is defined via singular attribute method like normal columns:

class DynamicColumnImportModel < DynamicColumnModel
  include CsvRowModel::Import

  # this is an override with the default implementation (override highly recommended)
  def skill(value, skill_name)
    value
  end

  class << self
    # Clean/format every dynamic_column attribute array
    #
    # this is an override with the default implementation
    def format_dynamic_column_cells(cells, column_name)
      cells
    end
  end
end
row_model = CsvRowModel::Import::File.new(file_path, DynamicColumnImportModel).next
row_model.attributes # => { first_name: "John", last_name: "Doe", skills: ['No', 'Yes'] }
row_model.skills # => ['No', 'Yes']

File Model (Mapping)

If you have to deal with a mapping on a csv you can use FileModel, isn't complete a this time and many cases isn't covered but can be helpful

Here an example of FileRowModel

class FileRowModel
  include CsvRowModel::Model
  include CsvRowModel::Model::FileModel

  row :string1
  row :string2, header: 'String 2'

  def self.format_header(column_name, context={})
    ":: - #{column_name} - ::"
  end
end

You can add format_header really helpful in case of I18n

you can pass header: option but we doesn't use it a the moment.

Import

In import mode we looking for the entries who match with the header, and we get the value in the same row in the right column.

i.e [Project Name, My Project]

If here Project Name is the header so value will be My Project

class FileImportModel < FileRowModel
  include CsvRowModel::Import
  include CsvRowModel::Import::FileModel
end

Export

In export mode you have to define template, this is more flexible than import. if you put and header, I mean in Symbol into the template, format_header will be call on it, so for I18n replacement is ok, for other cells you can ask the source_model or methods in the exporter

class FileExportModel < FileRowModel
  include CsvRowModel::Export
  include CsvRowModel::Export::FileModel

  def rows_template
    @rows_template ||= begin
      [
        [ :string1, ''  , string_value(1)                  ],
        [ 'String 2', '', ''             , ''              ],
        [ ''        , '', ''             , string_value(2) ],
      ]
    end
  end

  def string_value(number)
    source_model.string_value(number)
  end
end