class HexaPDF::Dictionary

Implementation of the PDF dictionary type.

Subclasses should use the available class method ::define_field to create fields according to the PDF specification. This allows, among other things, automatic type checking and basic validation.

Fields defined in superclasses are inherited by their subclasses. This avoids duplicating basic field information.

See: PDF1.7 s7.3.7

Public Class Methods

define_field(name, type:, required: false, default: nil, indirect: nil, allowed_values: nil, version: '1.0') click to toggle source

Defines an entry for the field name and returns the initalized HexaPDF::DictionaryFields::Field object. A suitable converter module (see HexaPDF::DictionaryFields::Field#converter) is selected based on the type argument.

Options:

type

The class (or an array of classes) that a value of this field must have. Here is a mapping from PDF object types to classes:

Boolean

[TrueClass, FalseClass] (or use the Boolean constant)

Integer

Integer

Real

Float

String

String (for text strings), PDFByteString (for binary strings)

Date

PDFDate

Name

Symbol

Array

PDFArray or Array

Dictionary

Dictionary (or any subclass) or Hash

Stream

Stream (or any subclass)

Null

NilClass

If an array of classes is provided, the value can be an instance of any of these classes.

If a Symbol object instead of a class is provided, the class is looked up using the 'object.type_map' global configuration option when necessary to support lazy loading.

Note that if multiple types are allowed and one of the allowed types is Dictionary (or a Symbol), it has to be the first in the list. Otherwise automatic type conversion functions won't work correctly.

required

Specifies whether this field is required.

default

Specifies the default value for the field, if any.

indirect

Specifies whether the value (or the values in the array value) of this field has to be an indirect object (true), a direct object (false) or if it doesn't matter (unspecified or nil).

allowed_values

An array of allowed values for this field.

version

Specifies the minimum version of the PDF specification needed for this value.

# File lib/hexapdf/dictionary.rb, line 98
def self.define_field(name, type:, required: false, default: nil, indirect: nil,
                      allowed_values: nil, version: '1.0')
  @fields ||= {}
  @fields[name] = Field.new(type, required: required, default: default, indirect: indirect,
                            allowed_values: allowed_values, version: version)
end
define_type(type) click to toggle source

Defines the static PDF type of the class in cases where this is possible, i.e. when the class implements one specific PDF type (e.g. the HexaPDF::Type::Catalog class).

# File lib/hexapdf/dictionary.rb, line 131
def self.define_type(type)
  @type = type
end
each_field {|name, data| block } → class click to toggle source
each_field → Enumerator

Calls the block once for each field defined either in this class or in one of the ancestor classes.

# File lib/hexapdf/dictionary.rb, line 123
def self.each_field(&block) # :yields: name, data
  return to_enum(__method__) unless block_given?
  superclass.each_field(&block) if self != Dictionary && superclass != Dictionary
  @fields.each(&block) if defined?(@fields)
end
field(name) click to toggle source

Returns the field entry for the given field name.

The ancestor classes are also searched for such a field entry if none is found for the current class.

# File lib/hexapdf/dictionary.rb, line 109
def self.field(name)
  if defined?(@fields) && @fields.key?(name)
    @fields[name]
  elsif superclass.respond_to?(:field)
    superclass.field(name)
  end
end
type() click to toggle source

Returns the statically defined PDF type of the class.

See ::define_type

# File lib/hexapdf/dictionary.rb, line 138
def self.type
  defined?(@type) && @type
end

Public Instance Methods

[](name) click to toggle source

Returns the value for the given dictionary entry.

This method should be used instead of direct access to the value because it provides numerous advantages:

  • References are automatically resolved.

  • Returns the native Ruby object for values with class HexaPDF::Object. However, all subclasses of HexaPDF::Object are returned as is (it makes no sense, for example, to return the hash that describes the Catalog instead of the Catalog object).

  • Automatically wraps hash values in specific subclasses of this class if field information is available (see ::define_field).

  • Returns the default value if one is specified and no value is available.

Note: If field information is available for the entry, a Hash or Array value will always be wrapped by Dictionary or PDFArray. Otherwise, the value will be returned as-is.

Note: This method may throw a “can't add a new key into hash during iteration” error in certain cases because it potentially modifies the underlying hash!

# File lib/hexapdf/dictionary.rb, line 163
def [](name)
  field = self.class.field(name)
  data = if key?(name)
           value[name]
         elsif field&.default?
           value[name] = field.default
         end
  value[name] = data = document.deref(data) if data.kind_of?(HexaPDF::Reference)
  if data.instance_of?(HexaPDF::Object) || (data.kind_of?(HexaPDF::Object) && data.value.nil?)
    data = data.value
  end
  if (result = field&.convert(data, document))
    self[name] = data = result
  end
  data
end
[]=(name, data) click to toggle source

Stores the data under name in the dictionary. Name has to be a Symbol object.

If the current value for this name has the class HexaPDF::Object (and only this, no subclasses) and the given value has not (including subclasses), the value is stored inside the HexaPDF::Object.

# File lib/hexapdf/dictionary.rb, line 185
def []=(name, data)
  unless name.kind_of?(Symbol)
    raise ArgumentError, "Only Symbol (Name) keys are allowed to be used in PDF dictionaries"
  end

  if value[name].instance_of?(HexaPDF::Object) && !data.kind_of?(HexaPDF::Object) &&
      !data.kind_of?(HexaPDF::Reference)
    value[name].value = data
  else
    value[name] = data
  end
end
delete(name) click to toggle source

Deletes the name-value pair from the dictionary and returns the value. If such a pair does not exist, nil is returned.

# File lib/hexapdf/dictionary.rb, line 205
def delete(name)
  value.delete(name) { nil }
end
each {|name, value| block} → dict click to toggle source
each → Enumerator

Calls the given block once for every name-value entry that is stored in the dictionary.

Note that the yielded value is already preprocessed like in [].

# File lib/hexapdf/dictionary.rb, line 216
def each
  return to_enum(__method__) unless block_given?
  value.each_key {|name| yield(name, self[name]) }
  self
end
empty?() click to toggle source

Returns true if the dictionary contains no entries.

# File lib/hexapdf/dictionary.rb, line 229
def empty?
  value.empty?
end
key?(key) click to toggle source

Returns true if the given key is present in the dictionary and not nil.

# File lib/hexapdf/dictionary.rb, line 199
def key?(key)
  !value[key].nil?
end
to_h() click to toggle source

Returns a dup of the underlying hash.

# File lib/hexapdf/dictionary.rb, line 234
def to_h
  value.dup
end
type() click to toggle source

Returns, in order or availability, the value of ::type, the /Type field or the result of Object#type.

Calls superclass method HexaPDF::Object#type
# File lib/hexapdf/dictionary.rb, line 224
def type
  self.class.type || self[:Type] || super
end

Private Instance Methods

each_set_key_or_required_field() { |name, field| ... } click to toggle source

Iterates over all currently set fields and those that are required.

# File lib/hexapdf/dictionary.rb, line 262
def each_set_key_or_required_field #:yields: name, field
  value.keys.each {|name| yield(name, self.class.field(name)) }
  self.class.each_field do |name, field|
    yield(name, field) if field.required? && !value.key?(name)
  end
end
perform_validation() { |"Required field #{name} is not set", default?| ... } click to toggle source

Performs validation tasks based on the currently set keys and defined fields.

Calls superclass method HexaPDF::Object#perform_validation
# File lib/hexapdf/dictionary.rb, line 270
def perform_validation(&block)
  super
  each_set_key_or_required_field do |name, field|
    obj = key?(name) ? self[name] : nil

    # The checks below need a valid field definition
    next if field.nil?

    # Check that required fields are set
    if field.required? && obj.nil?
      yield("Required field #{name} is not set", field.default?)
      self[name] = obj = field.default if field.default?
    end

    # Check if the document version is set high enough
    if field.version > document.instance_variable_get(:@version)
      yield("Field #{name} requires document version to be #{field.version}", true)
      document.version = field.version
    end

    # The checks below assume that the field has a value
    next if obj.nil?

    # Check the type of the field
    unless field.valid_object?(obj)
      msg = "Type of field #{name} is invalid: #{obj.class}"
      if field.type.include?(String) && obj.kind_of?(Symbol)
        yield(msg, true)
        self[name] = obj.to_s
      elsif field.type.include?(Symbol) && obj.kind_of?(String)
        yield(msg, true)
        self[name] = obj.intern
      else
        yield(msg, false)
      end
    end

    # Check the value of the field against the allowed values.
    if field.allowed_values && !field.allowed_values.include?(obj)
      yield("Field #{name} does not contain an allowed value: #{obj.inspect}")
    end

    # Check if field value needs to be (in)direct
    unless field.indirect.nil?
      obj = value[name] # we need the unwrapped object!
      if field.indirect && (!obj.kind_of?(HexaPDF::Object) || !obj.indirect?)
        yield("Field #{name} needs to be an indirect object", true)
        value[name] = document.add(obj)
      elsif !field.indirect && obj.kind_of?(HexaPDF::Object) && obj.indirect?
        yield("Field #{name} needs to be a direct object", true)
        document.delete(obj)
        value[name] = obj.value
      end
    end
  end
end
set_required_fields_with_defaults() click to toggle source

Sets all required fields that have no current value but a default value to their respective default value.

# File lib/hexapdf/dictionary.rb, line 253
def set_required_fields_with_defaults
  self.class.each_field do |name, field|
    if !key?(name) && field.required? && field.default?
      value[name] = field.default
    end
  end
end