Classdef get methods: allowing get indexing into an array of length either (1x1) or (Nx1).

2 ビュー (過去 30 日間)
Hello all, I am trying to sort out an issue best shown in this MWE, where I have a property that may be a column vector, but is initialized with a single value.
classdef myClass
properties
A (:,1) double = 0;
end
methods
end
end
Now, lets say I want to index into myClass.A using B = myClass.A(indx). However, I want it so that if myClass.A is still a (1x1) I want to return the initial value, not an "Index exceeds array bounds" error.
I can picture doing this with a get method of the following form
function out = get.A(indx)
if numel(obj.A) == 1
out = obj.A(1);
else
out = obj.A(indx);
end
end
However, this will clearly not work since (A) get methods are limitited to one input, and I need to pass "indx", (B) I don't pass an instance of the object to get.A, so it has no access, and (C) this would wind up being infinitely recursive if I was able to do it.
SO:
Is there a way to allow use of a single default value as the output of a property regardless of the requested index, if that property has not yet been overwritten with an Nx1 vector.
Cheers,
DP

採用された回答

Catalytic
Catalytic 2019 年 3 月 27 日
編集済み: Catalytic 2019 年 3 月 27 日
You would need to overload subsref, e.g.,
methods
function out=subsref(obj,S)
if S(1).type=="." && S(1).subs{1}=="A" && numel(S)>1
out=obj.A(min(S(2).subs{1},1));
else
error 'Undefined Indexing'
end
end
end
  1 件のコメント
D. Plotnick
D. Plotnick 2019 年 3 月 28 日
Darn. I was hoping someone had another idea in the last day, because I really don't want to overload subsref or any other low level Matlab functions. Thanks for the input, I hadn't even thought of that, I may just need to bite the bullet and put the check:
if indx > length(obj.A)
indx = 1;
end
val = obj.A(indx);
into all of the higher level functions, rather than something in the class definition itself.

サインインしてコメントする。

その他の回答 (1 件)

Sean de Wolski
Sean de Wolski 2019 年 3 月 28 日
編集済み: Sean de Wolski 2019 年 3 月 28 日
You could GetAccess Protect the A property and then use a method instead of straight property reference.
methods
function a = getA(obj, indx)
if numel(obj.A) == 1 || nargin == 1
out = obj.A(1);
else
out = obj.A(indx);
end
end
end
  1 件のコメント
D. Plotnick
D. Plotnick 2019 年 3 月 28 日
Thanks. That is indeed less invasive than overloading subsref.

サインインしてコメントする。

カテゴリ

Help Center および File ExchangeEvents についてさらに検索

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by