图形对象的父级在parfor中无法读取

在parfor中，我无法通过 h.Parent() 的方式读取到图形对象的父对象，使用 ancestor(h, "Figure") 方法同样不行，这是为什么？

H = gobjects(3, 1);
figure("Name", "fig1", Visible="off"), H(1) = axes(); plot(1:10);
figure("Name", "fig2", Visible="off"), H(2) = axes(); plot(1:10);
figure("Name", "fig3", Visible="off"), H(3) = axes(); plot(1:10);

% for-loop
for i = 1:3
    disp(class(H(i)));  % matlab.graphics.axis.Axes
    disp(class(H(i).Parent));   % matlab.ui.Figure
    disp(class(ancestor(H(i), "figure")));  % matlab.ui.Figure
    disp(H(i).Parent.Name); % Fig i
end

matlab.graphics.axis.Axes

matlab.ui.Figure

matlab.ui.Figure

fig1

matlab.graphics.axis.Axes

matlab.ui.Figure

matlab.ui.Figure

fig2

matlab.graphics.axis.Axes

matlab.ui.Figure

matlab.ui.Figure

fig3

% parfor-loop
parfor i = 1:3
    disp(class(H(i)));  % matlab.graphics.axis.Axes
    disp(class(H(i).Parent));   % matlab.graphics.GraphicsPlaceholder, why?
    disp(class(ancestor(H(i), "figure")));  % double, why?
    disp(H(i).Parent.Name); % error
end

Starting parallel pool (parpool) using the 'Processes' profile ...
Connected to the parallel pool (number of workers: 2).
matlab.graphics.axis.Axes
matlab.graphics.GraphicsPlaceholder
double
matlab.graphics.axis.Axes
matlab.graphics.GraphicsPlaceholder
double

Unrecognized method, property, or field 'Name' for class 'matlab.graphics.GraphicsPlaceholder'.

Answer 1

[Himanshu]

Hello,

As per my understanding, you are facing an error while using "parfor" loop and reading the parent of a graphical object. The error occurs because accessing the properties of the parent figure or working with graphical objects directly is not supported within "parfor" loops.

When using "parfor" in MATLAB, graphical objects behave differently than in a regular "for" loop due to the nature of parallel computing. In a "parfor" loop, MATLAB creates separate worker instances that execute the loop iterations independently and in parallel. Each worker has its own workspace and does not have access to the GUI.

You can refer to the below documentation to understand more about "parfor" loops.

Parallel for-loop - MATLAB parfor - MathWorks India

Execute for-loop iterations in parallel on workers - MATLAB parfor - MathWorks India

Decide When to Use parfor - MATLAB & Simulink - MathWorks India