Class: Redlander::Statement

Inherits:
Object
  • Object
show all
Defined in:
lib/redlander/statement.rb

Overview

RDF statement

Instance Method Summary collapse

Constructor Details

#initialize(source = {}) ⇒ Statement

Create an RDF statement.

Parameters:

  • source (Hash) (defaults to: {})

Options Hash (source):

  • :subject (Node, String, URI, nil)
  • :predicate (Node, String, URI, nil)
  • :object (Node, String, URI, nil)

Raises:

  • (NotImplementedError) —

    if cannot create a Statement from the given source.

  • (RedlandError) —

    if it fails to create a Statement.



42
43
44
45
46
 
# File 'lib/redlander/statement.rb', line 42

def initialize(source = {})
  # If FFI::Pointer is passed, wrap it instantly,
  # because it can be freed outside before it is used here.
  @source = source.is_a?(FFI::Pointer) ? wrap(source) : source
end

Instance Method Details

#eql?(other_statement) ⇒ Boolean Also known as: ==

Returns:

  • (Boolean) 


111
112
113
114
115
 
# File 'lib/redlander/statement.rb', line 111

def eql?(other_statement)
  subject == other_statement.subject &&
    predicate == other_statement.predicate &&
    object == other_statement.object
end

#hash ⇒ Object 



118
119
120
 
# File 'lib/redlander/statement.rb', line 118

def hash
  self.class.hash + to_s.hash
end

#object ⇒ Node?

Object of the statement.

Returns:



75
76
77
78
79
80
81
82
 
# File 'lib/redlander/statement.rb', line 75

def object
  if instance_variable_defined?(:@object)
    @object
  else
    rdf_node = Redland.librdf_statement_get_object(rdf_statement)
    @object = rdf_node.null? ? nil : Node.new(rdf_node)
  end
end

#object=(node) ⇒ void

This method returns an undefined value.

Set the object of the statement

Parameters:



106
107
108
109
 
# File 'lib/redlander/statement.rb', line 106

def object=(node)
  Redland.librdf_statement_set_object(rdf_statement, rdf_node_from(node))
  @object = node
end

#predicate ⇒ Node?

Predicate of the statement.

Returns:



63
64
65
66
67
68
69
70
 
# File 'lib/redlander/statement.rb', line 63

def predicate
  if instance_variable_defined?(:@predicate)
    @predicate
  else
    rdf_node = Redland.librdf_statement_get_predicate(rdf_statement)
    @predicate = rdf_node.null? ? nil : Node.new(rdf_node)
  end
end

#predicate=(node) ⇒ void

This method returns an undefined value.

Set the predicate of the statement

Parameters:



97
98
99
100
 
# File 'lib/redlander/statement.rb', line 97

def predicate=(node)
  Redland.librdf_statement_set_predicate(rdf_statement, rdf_node_from(node))
  @predicate = node
end

#rdf_statement ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future. 



14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
 
# File 'lib/redlander/statement.rb', line 14

def rdf_statement
  unless instance_variable_defined?(:@rdf_statement)
    @rdf_statement = case @source
                     when FFI::Pointer
                       @source
                     when Hash
                       # Create a new statement from nodes
                       s = rdf_node_from(@source[:subject])
                       p = rdf_node_from(@source[:predicate])
                       o = rdf_node_from(@source[:object])
                       Redland.librdf_new_statement_from_nodes(Redlander.rdf_world, s, p, o)
                     else
                       raise NotImplementedError, "Cannot create Statement from '#{@source.inspect}'"
                     end
    raise RedlandError, "Failed to create a new statement" if @rdf_statement.null?
    ObjectSpace.define_finalizer(self, self.class.send(:finalize_statement, @rdf_statement))
  end
  @rdf_statement
end

#subject ⇒ Node?

Subject of the statment.

Returns:



51
52
53
54
55
56
57
58
 
# File 'lib/redlander/statement.rb', line 51

def subject
  if instance_variable_defined?(:@subject)
    @subject
  else
    rdf_node = Redland.librdf_statement_get_subject(rdf_statement)
    @subject = rdf_node.null? ? nil : Node.new(rdf_node)
  end
end

#subject=(node) ⇒ void

This method returns an undefined value.

Set the subject of the statement

Parameters:



88
89
90
91
 
# File 'lib/redlander/statement.rb', line 88

def subject=(node)
  Redland.librdf_statement_set_subject(rdf_statement, rdf_node_from(node))
  @subject = node
end

#to_s ⇒ Object 



122
123
124
 
# File 'lib/redlander/statement.rb', line 122

def to_s
  Redland.librdf_statement_to_string(rdf_statement)
end