Optional Class Reference
Inherits from |
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Declared in |
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template <class T> class Optional; |
flip::Optional
is a zero or one element constrained container.
The Optional
itself provides support for modification introspection. When modifying the content of the Optional
, the previous representation of the optional is still present.
Internally the Optional
is just a Collection
with a constraint on size.
Template Parameters
| The type of the elements. |
Member Types
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Member Functions Synopsys
Constructs the | |
Destructs the | |
Assigns values to the container |
Document Management
Returns the document to which the object is attached to | |
Returns the unique reference number of the object | |
Returns | |
Returns | |
Returns | |
Returns | |
Returns a reference to a parent in the current parent chain of the object | |
Disables the record state modification in history | |
Inherits the record state modification in history | |
Returns | |
Reverts all the changes made to the object and its children if any | |
Replaces the content of the object with the content of the provided object |
Element Access
Access element | |
Access element | |
Access previous version of element |
Modifiers
Resets element in-place |
Observers
Returns true iff empty | |
Returns true iff empty |
Member Functions
Constructor
Optional (); (1) |
Optional (const Optional & other); (2) |
- Default constructor, constructs an empty optional.
- Copy constructor. Constructs the container with copy of elements of
other
.
Destructor
~Optional (); |
Destructor.
operator =
Optional & operator = (const Optional & other); |
template <class U> |
Optional & operator = (const U & other); |
Copy assignment operator.
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 a reference to the element.
use
template <class U> |
U & use () const; |
Returns a reference to the element as type U
.
before
T & before () const; |
template <class U> |
U & before () const; |
Returns a reference to previous version of the element.
reset
void reset (None); (1) |
template <class... Args> |
T & reset (Args &&... args); (2) |
template <class U, class... Args> |
U & reset (Args &&... args); (3) |
T & reset (const Mold & mold); (4) |
template <class U> |
U & reset (const Mold & mold); (5) |
- Resets to empty by writing
optional.reset (flip::None)
- Resets to a new element constructed in-place with arguments
args
. - Resets to a new element of type
U
constructed in-place with argumentsargs
. - Resets to a new element casted from
mold
. - Resets to a new element of type
U
casted frommold
.
empty
bool empty () const; |
Returns true iff empty.
operator bool
explicit operator bool () const; |
Returns true iff the optional contains an element.