Redland RDF Application Framework - Ruby RDoc

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Class

Redland::Statement

In:

Parent:

Object

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}"

Methods

== create_finalizer new object object= predicate predicate= subject subject= to_s

Included Modules

Util

Attributes

statement [R] the internal librdf statement

Public Class methods

create_finalizer(statement)

You shouldn‘t use this. Used internally for cleanup.

[Source]

# 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)

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

[Source]

# 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)

Equivalency. Only works for comparing two Statements

[Source]

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

object()

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

[Source]

# 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)

set the object of the statement

[Source]

# 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()

return the predicate of the statement triple.

[Source]

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

predicate=(value)

set the predicate of the statement

[Source]

# 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()

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

[Source]

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

subject=(value)

set the subject of the statement

[Source]

# 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()

Convert this Statement to a string

[Source]

# 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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