Flip Reference

ObjectRef Class Reference

Inherits from

BasicType

Declared in

flip/ObjectRef.h

template <class T>   class ObjectRef;

flip::ObjectRef is a type that represents a pointer or reference to an actual flip object.

Internally it stores a flip unique reference number (see flip::Ref for more details)

Therefore, getting a potentially associated object can be done in a safe way.

It is perfectly valid to have a flip::ObjectRef pointing to a reference which is no longer in the model. In this case accessing the underlying object will return nullptr.

It only provides a convenient interface to store a flip::Ref into the model and a way to dereference it safely.

Important: In particular, unlike containers, an ObjectRef won't have a changed state when the pointee element is changed.

Template Parameters

T

The type of the elements. T must inherit from flip::Object

Member Functions Synopsys

Constructor

Constructs the ObjectRef

Destructor

Destructs the ObjectRef

operator =

Assigns value

Document Management

document

Returns the document to which the object is attached to

ref

Returns the unique reference number of the object

added

Returns true iff the object was just attached to the document tree

removed

Returns true iff the object was just detached from the document tree

resident

Returns true iff the object was neither attached nor detached from the document tree

changed

Returns true iff the object or one of its children was modified

ancestor

Returns a reference to a parent in the current parent chain of the object

disable_in_undo

Disables the record state modification in history

inherit_in_undo

Inherits the record state modification in history

is_in_undo_enabled

Returns true iff this object modifications are recorded in history

revert

Reverts all the changes made to the object and its children if any

assign

Replaces the content of the object with the content of the provided object

Value Access

operator T *

Returns the current value of the object

get

Returns the current value of the object as a flip unique reference number

before

Returns the previous value of the object

get_before

Returns the previous value of the object as a flip unique reference number

Comparaison

operator ==

Returns true iff objects current values are equal

operator !=

Returns true iff objects current values are different

Member Functions

Constructor

ObjectRef ();                          (1)
ObjectRef (const ObjectRef & other);   (2)
ObjectRef (T * ptr);                   (3)
ObjectRef (const Ref & ref);           (4)
  1. Default constructor, constructs with a nullptr value.
  2. Copy constructor. Constructs the object with the value of other.
  3. Constructor. Constructs the object with pointer ptr.
  4. Constructor. Constructs the object with a flip unique reference number.

WARNING: Variant 3 and 4 of the constructor cannot be called from the default constructor of a flip object.


Destructor

~ObjectRef ();

Destructor.


operator =

ObjectRef & operator = (const ObjectRef & other);  (1)
ObjectRef & operator = (T * ptr);                  (2)
ObjectRef & operator = (const Ref & ref);          (3)
  1. Copy assignment operator.
  2. Assignment operator. Assigns the object with pointer ptr.
  3. Assignment operator. Assigns the object with a flip unique reference number.

document

DocumentBase & document () const;

Returns the document to which the object is attached to.

WARNING: Temporary flip objects are not attached to a document


ref

const Ref & ref () const;

Returns the unique reference number of the object.


added

bool  added () const;

Returns true iff the object was just attached to the document tree.

Example :

void  Observer::document_changed (Note & note)
{
   if (note.added ())
   {
      // A note was added to the document. Create the corresponding
      // view element
      note.entity ().emplace <NoteView> ();
   }
   [...]
}

removed

bool  removed () const;

Returns true iff the object was just detached from the document tree.

Example :

void  Observer::document_changed (Note & note)
{
   [...]
   if (note.removed ())
   {
      // A note was removed from the document. Release the corresponding
      // view element
      note.entity ().erase <NoteView> ();
   }
}

resident

bool  resident () const;

Returns true iff the object was neither attached nor detached from the document tree.

An object can be resident but moved. In this case the iterator pointing to it will allow to detect the move.

Example :

void  Observer::document_changed (Array <Track> & tracks)
{
   auto it = tracks.begin ();
   auto it_end = tracks.end ();
   for (; it != it_end ; ++it)
   {
      Track & track = *it;
      if (it.added () && track.resident ())
      {
         // the track was moved in the container
         // this is the destination position
      }
      if (it.added () && track.resident ())
      {
         // the track was moved in the container
         // this is the source position
      }
   }
}

changed

bool  changed () const;

Returns true iff the object or one of its children was modified.

Example :

void  Observer::document_changed (Note & note)
{
   auto & view = note.entity ().use <ViewNote> ();
   if (note.changed ())
   {
      // one or more properties of the note changed
      if (note.position.changed ())
      {
         view.set_position (note.position);
      }
      if (note.duration.changed ())
      {
         view.set_duration (note.duration);
      }
   }
}

ancestor

template <class T>   T &   ancestor ();
template <class T>   const T &   ancestor () const;

Returns a reference to a parent in the current parent chain of the object.

Note: If an object or its parent is moved from one container to another, this function will always return the current parent, that is not the previous one


disable_in_undo

void   disable_in_undo ();

Disables the record state modification in history of the object and its subtree if any.

Example :

void  add_user (Root & root)
{
   // emplace a new User of the document to store
   // user specific data. User is constructed with
   // the unique user id number given at document
   // creation
   User & user = root.users.emplace <User> (root.document ().user ());
   // we don't want the scroll position in the document
   // to be part of undo
   user.scroll_position.disable_in_undo ();
}

inherit_in_undo

void   inherit_in_undo ();

Inherits the record state modification in history of the object and its subtree if any, from its parent state. This is the default mode.

Note: If the Root object of the tree is in inherited mode, then it is considered as enabled in undo.


is_in_undo_enabled

bool  is_in_undo_enabled () const;

Returns true iff this object modifications are recorded in history. The function recursively search for disabled state starting from the object itself and navigating through the parent objects, if the state is inherited.


revert

void  revert () const;

Reverts all the changes make to the object and its children if any.

Example :

// initially, note.position == 1
note.position = 2;
note.revert ();
// now, note.position == 1

assign

void  assign (const Type & rhs);

Replaces the content of the object with the content of the provided object. Both objects need to be bound to a document for the function to succeed.

Example :

// initially :
// note.position == 1
// note.duration == 3
// note2.position == 2
// note2.duration == 1
note.assign (note2);
// now :
// note.position == 2
// note.duration == 1

operator T *

operator T * () const;

Returns the current value of the object or nullptr, if the referenced object does not exist anymore.


get

Ref   get () const;

Returns the current value of the object as a flip unique reference number, even if the object does not exist anymore.


before

T *  before () const;

Returns the previous value of the object or nullptr, if the referenced object does not exist anymore.


get_before

Ref   get_before () const;

Returns the previous value of the object as a flip unique reference number, even if the object does not exist anymore.


operator ==

bool  operator == (const ObjectRef & rhs) const;
bool  operator == (T * rhs) const;

operator !=

bool  operator != (const ObjectRef & rhs) const;
bool  operator != (T * rhs) const;