1. @ReferAssignGetSet February 21, 2008 http://jagger. me. berkeley
@ReferAssignGetSet February 21, Copyright , Andy Packard. This work is licensed under the Creative Commons Attribution-ShareAlike License. To view a copy of this license, visit or send a letter to Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA.

2. @ReferAssignGetSet Many ideas of
get, set, subsref, subsasgn
will to carry over to all classes we write. For example,
Reference of M.Value is the same as get(M,’Value’)
Multi-depth subsref has specific recursive meaning
Assignment of M.Value=B is the same as set(M,’Value’,B)
Multi-depth subsasgn has specific recursive meaning
In some cases, () reference and assignment should be handled by the built-in methods for Matlab arrays
set should work with or without output arguments
Special Matlab-like conventions for get and set should be followed
Calls with 1-input argument
Property names can be partially specified
Multiple args in set(A,P1,V1,P2,V2)
This is a good motivation to write a class that handles all of this functionality, and all other classes will simply inherit this.

3. @ReferAssignGetSet Questions/Options for a given class
Is property reference allowed, as in Object.Property
Is property assignment allowed, as in Object.Property = Value
Is () reference allowed, as in Object(Idx1,Idx2)
if so, are builtin methods used, or does the class programmer supply the reference method?
Is () assignment allowed, as in Object(Idx1,Idx2) = Value
if so, are builtin methods used, or does the class programmer supply the assignment method?
Is {} reference allowed, as in Object{Idx1,Idx2}
Is {} assignment allowed, as in Object{Idx1,Idx2} = Value
Does set use assignin when called with no output arguments?
set(A,Prop,Value) %uses inputname, overwrites A
A = set(A,Prop,Value) % overwrites A, directly
B = set(A,Prop,Value) % A unchanged

4. @ReferAssignGetSet
Constructor (see actual code) just keeps track of the options to handle decisions for each of the cases described.
function A = ReferAssignGetSet(InputArgsSpecifiers)
A.PropertyRef = 'followGet'; % or 'disallow'
A.PropertyAssign = 'followSet'; % 'disallow'
A.ParenRef = 'ProgSupplied'; % 'builtin', 'disallow'
A.ParenAssign = 'ProgSupplied'; % 'builtin', 'disallow'
A.BraceRef = 'ProgSupplied'; % 'builtin', 'disallow'
A.BraceAssign = 'ProgSupplied'; % 'builtin', 'disallow'
A.AllowSetAssignin = 0; % or 1
A = class(A,'ReferAssignGetSet');
Also need general purpose versions of
get, set, subsref, subsasgn

5. Folder layout @ReferAssignGetSet @class1 @class2 @class3 private
ReferAssignGetSet.m
get.m
set.m
subsref.m
subsasgn.m
fieldnames.m
class1.m
GetSetPropertyInfo
isvalid
PrivateGet
PrivateSet
ParenthesisReference
ParenthesisAssign
BraceReference
BraceAssign
horzcat, vertcat
smartpropmatch
private
@ReferAssignGetSet
class2.m
GetSetPropertyInfo
Isvalid
PrivateGet
PrivateSet
ParenthesisReference
ParenthesisAssign
OtherMethodsforclass2
@class1
class3.m
GetSetPropertyInfo
Isvalid
PrivateGet
PrivateSet
OtherMethodsforclass3
@class2
@class3

6. Example child class: @point
function A = point(X,Y,varargin)
S.X = X; S.Y = Y; % point in 2-dim Euclidean space
PropRef = 'followGet'; % or 'disallow'
PropAssign = 'followSet'; % or 'disallow'
ParenRef = 'builtin'; % or 'builtin' or 'disallow'
ParenAssign = 'builtin'; % or 'builtin' or 'disallow'
BraceRef = 'disallow'; % or 'ProgSupplied' or 'builtin'
BraceAssign = 'disallow'; %or 'ProgSupplied‘, 'builtin'
ASA = 1; % or 0, ASA-> AllowSetAssignin
B = ReferAssignGetSet(PropRef,PropAssign,...
ParenRef,ParenAssign,BraceRef,BraceAssign,ASA);
A = class(S,'point',B);
lvin = length(varargin);
if lvin>0 && ceil(lvin/2)==floor(lvin/2)
A = set(A,varargin{:});
end

7. @ReferAssignGetSet get and set call the child’s GetSetPropertyInfo
function [GPN,SPN,SPD] = GetSetPropertyInfo(A)
% Return a N-by-1 cell array of GET Prop Names
% Return a M-by-1 cell array of SET Prop Names
% Return a M-by-1 cell array of SET Property
% Descriptions
get & set also call child’s PrivateGet and PrivateSet
function Value = PrivateGet(Object,GPropName)
function B = PrivateSet(Object,SPropName,Value)

8. @point/GetSetPropertyInfo.m
function [GPN,SPN,SPD] = GetSetPropertyInfo(A)
CommonNames = {'XCoord';'YCoord'};
OnlyGet = {'Radius';'Angle'};
OnlySet = cell(0,1); % empty cell
GPN = [CommonNames;OnlyGet]; % gettable properties
SPN = [CommonNames;OnlySet]; % settable properties
SPD = {'XCoordinate of Point';'YCoordinate of Point'};

9. Pseudocode for get.m function V = get(A,Property)
[GPN,SPN,SPD] = GetSetPropertyInfo(A);
if nargin==2
FullPropName = smartpropmatch(Property,GPN);
V = PrivateGet(A,FullPropName);
else % nargin==1
% Create structure V1 with fieldnames equal
% to the property names in GPN. Then fill
% the values of the struct with the values
% calling PrivateGet.
if nargout==1; V = V1;
else; disp(V1)
end

10. Pseudocode for PrivateGet.m
function V = PrivateGet(A,FullPropName)
switch FullPropName
case PropertyName1
V = % extract Property1 from fields of A
case PropertyName2
V = % extract Property2 from fields of A
case ...
case PropertyNameK
V = % extract PropertyK from fields of A
Otherwise
error(’Unknown Property’);
end

11. @point/PrivateGet.m function V = PrivateGet(A,FullPropName)
switch FullPropName
case 'XCoord'
V = A.X;
case 'YCoord'
V = A.Y;
case 'Radius'
V = norm([A.X A.Y]);
case 'Angle'
V = atan2(A.Y,A.X);
otherwise
error([FullPropName ': Unknown Property.']);
end

12. @point/PrivateSet.m function A = PrivateSet(A,FullPropName,Value)
switch FullPropName
case 'XCoord'
if isa(Value,'double') && isscalar(Value)
A.X = Value;
else
error('XCoordinate should be real scalar');
end
case 'YCoord'
A.Y = Value;
error('YCoordinate should be real scalar');
otherwise
error([FullPropName ': Unknown Property']);

13. Similar for Assignment/Reference
General purpose subsref, subsasgn
reside
they call the object’s specific reference and assignment methods
ParenthesisAssign
ParenthesisReference
BraceAssign
BraceReference
In this way, one version of subsref and subsasgn address the issues
Proper relation to get/set
Deep references/assignments
Similarly, there should be tight integration with horzcat and vertcat, but at this point, we leave that to the programmer...

14. @ReferAssignGetSet/subsref
function B = subsref(A,L)
ReAsGeSe = A(1);
switch L(1).type
case '.'
if isequal(ReAsGeSe.PropertyRef,'followGet')
B = get(A,L(1).subs);
else
error('dot(.) reference not allowed. Use GET.');
end
case '()'
case '{}'
if length(L)>1
B = subsref(B,L(2:end));

15. @ReferAssignGetSet/subsref
function B = subsref(A,L)
ReAsGeSe = A(1);
switch L(1).type
case '.'
case '()'
if isequal(ReAsGeSe.ParenRef,'builtin')
B = builtin('subsref',A,L(1));
elseif isequal(ReAsGeSe.ParenRef,'ProgSupplied')
B = ParenthesisReference(A,L(1).subs);
else
error('() reference is not allowed.');
end
case '{}'
if length(L)>1
B = subsref(B,L(2:end));

16. @ReferAssignGetSet/subsref
function B = subsref(A,L)
ReAsGeSe = A(1);
switch L(1).type
case '.'
case '()'
case '{}'
if isequal(ReAsGeSe.BraceRef,'builtin')
B = builtin('subsref',A,L(1));
elseif isequal(ReAsGeSe.BraceRef,'ProgSupplied')
B = BraceReference(A,L(1).subs);
else
error('{} reference is not allowed.');
end
if length(L)>1
B = subsref(B,L(2:end));

17. @ReferAssignGetSet/subsasgn
function B = subsasgn(A,L,RHS)
ReAsGeSe = A(1);
switch L(1).type
case '.'
if isequal(ReAsGeSe.PropertyAssign,'followSet')
if length(L)==1
B = set(A,L(1).subs,RHS);
else
tmp = get(A,L(1));
tmp = subsasgn(tmp,L(2:end),RHS);
B = set(A,L(1).subs,tmp);
end
error('dot(.) assignment not allowed. Use SET.');
othercases

18. @ReferAssignGetSet/subsasgn
case '()'
if isequal(ReAsGeSe.ParenAssign,'builtin')
if length(L)==1
B = builtin('subsasgn',A,L(1),RHS);
else
tmp = builtin('subsref',A,L(1));
tmp = subsasgn(tmp,L(2:end),RHS);
B = builtin('subsasgn',A,L(1),tmp);
end
elseif isequal(ReAsGeSe.ParenAssign,'ProgSupplied')
B = ParenthesisAssign(A,L(1).subs,RHS);
tmp = subsref(A,L(1));
B = ParenthesisAssign(A,L(1).subs,tmp);
error('() assignment is not allowed.');

19. Examples using @point (try these)
>> p = point(2,4);
>> get(p)
>> get(p,’Radius’)
>> p.Angle
>> p.An
>> get(p,’Angle’)
>> p.XCoord = 4;
>> p.Angle*180/pi % convert to degrees
>> set(p)
>> p2 = point(-5,10);
>> M = [p p2;point(1,1) point(3,-3)];
>> M(2,1).XCoord
>> M(2,1).XCo = 3;
>> M(2,1).An
Why do these work?
New Challenge: After you check these commands out, make Radius and Angle settable. Rule would be that when you change Radius, the Angle is unchanged, and similar for changing Angle. In each case, the underlying “real” data (X and Y) have to get correctly modified.