Redland::Statement

Redland Statement (triple class). The main means of manipulating statements is by the subject,predicate,and object properties

require 'rdf'
Statement creation from nodes
statement1 = Statement.new(node1,node2,node3)
statement2 = Statement.new(:statement=>statement)

if statement2.resource?
  puts "statement2.subject has uri #{statement2.subject.uri}"

Attributes

statement[R]

the internal librdf statement

Public Class Methods

create_finalizer(statement) click to toggle source

You shouldn't use this. Used internally for cleanup.

# File rdf/redland/statement.rb, line 70
def Statement.create_finalizer(statement)
  proc {|id| Redland::librdf_free_statement(statement) }
end

new(subject=nil,predicate=nil,object=nil,model=nil) click to toggle source

create a new Statement with subject,predicate,and object the subject, predicate, and objects can be of class String or Uri.

# File rdf/redland/statement.rb, line 25
def initialize(subject=nil,predicate=nil,object=nil,model=nil)
  @model = model
  
  if subject.class == Hash
    if subject.key?(:from_object)
      @statement = Redland.librdf_new_statement_from_statement(subject[:from_object])
      @model = subject[:model]
    end
  else
    
    unless subject
      s = nil
    else
      if (subject.class == Uri)|| (subject.class == String)
        subject = Node.new(subject)
      end
      s = Redland.librdf_new_node_from_node(subject.node)
    end
    
    unless predicate
      p = nil
    else    
      if (predicate.class == Uri) || (predicate.class == String)
        predicate = Node.new(predicate)
      end
      p = Redland.librdf_new_node_from_node(predicate.node)
    end

    unless object
      o = nil
    else    
      if (object.class == Uri) || (object.class == String)
        object = Node.new(object)
      end
      o = Redland.librdf_new_node_from_node(object.node)
    end
    @statement = Redland.librdf_new_statement_from_nodes($world.world,s,p,o)
  end

  raise RedlandError.new("Statement construction failed") if !@statement
  ObjectSpace.define_finalizer(self,Statement.create_finalizer(@statement))

end

Public Instance Methods

==(other) click to toggle source

Equivalency. Only works for comparing two Statements

# File rdf/redland/statement.rb, line 140
def ==(other)
  return (Redland.librdf_statement_equals(self.statement,other.statement) != 0)
end

object() click to toggle source

return the object of the statement triple. The return value is either a Literal or Resource depending if object returned from the store is literal or not

# File rdf/redland/statement.rb, line 94
def object()
  object_node = Redland.librdf_statement_get_object(self.statement)
  return Literal.from_node(object_node) if is_literal?(object_node)
  return Resource.new(object_node,@model)
end

object=(value) click to toggle source

set the object of the statement

# File rdf/redland/statement.rb, line 111
def object=(value)
  if value
    Redland.librdf_statement_set_object(self.statement,
                                        Redland.librdf_new_node_from_node(value.node))
  else
    Redland.librdf_statement_set_object(self.statement, nil)
  end
end

predicate() click to toggle source

return the predicate of the statement triple.

# File rdf/redland/statement.rb, line 87
def predicate()
  return wrap_node(Redland.librdf_statement_get_predicate(self.statement))
end

predicate=(value) click to toggle source

set the predicate of the statement

# File rdf/redland/statement.rb, line 121
def predicate=(value)
  if value
    Redland.librdf_statement_set_predicate(self.statement,
                                           Redland.librdf_new_node_from_node(value.node))
  else
    Redland.librdf_statement_set_predicate(self.statement, nil)
  end
end

subject() click to toggle source

return the subject of the statement triple. The subject is of class Resource

# File rdf/redland/statement.rb, line 82
def subject()
  return Resource.new(Redland.librdf_statement_get_subject(self.statement),@model)
end

subject=(value) click to toggle source

set the subject of the statement

# File rdf/redland/statement.rb, line 101
def subject=(value)
  if value
    Redland.librdf_statement_set_subject(self.statement,
                                         Redland.librdf_new_node_from_node(value.node))
  else
    Redland.librdf_statement_set_subject(self.statement, nil)
  end
end

to_s() click to toggle source

Convert this Statement to a string

# File rdf/redland/statement.rb, line 131
def to_s()
  unless self.statement
    raise RedlandError.new("Statement is invalid")
  else
    return Redland.librdf_statement_to_string(self.statement)
  end
end

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Redland::Statement

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