Conversion from logical no longer works in MATLAB 2015a

Hello,

I have a function that worked in MATLAB 2014a but that no longer works in MATLAB 2015a.

if hw && ishandle(hw)

hw is a uicontrol, the error message returned is listed below.

Conversion to logical from matlab.ui.control.UIControl is not possible.

Can you tell me what has changed in 2015a to cause this error?

Thanks.

Answer 1

[Adam]

You should use

ishghandle(...)

for graphics handle objects, but if hw is a graphics handle object then I'm not sure what you expect it to be on implicit conversion to a logical type.

In previous versions all graphics handles where doubles, but now they are actual class objects so the above function will test if it is a valid graphics handle or not.

Also

isgraphics(...)

and

isvalid(...)

seem to do very similar tests. I always forget the subleties of their usage as I always use ishghandle to test, for example, that an axes is valid before using it.

[Nick]

Thanks!

[Walter Roberson]

Before "if hw" would be checking to see if hw was anything other than 0. A handle could be 0 if it was the graphics root, now called groot. Or a handle could be 0 if the program had deliberately zeroed it to indicate that it was no longer valid, which is a mixup between Value and State that has come back to bite the programmer in the Fundament(al Datatypes)