I'm using R2019b.
I have created a GUI app using appdesigner and have written the function testFun in a m-file (testFun should also be usable by a non GUI approach, hence the m-file).
Within the app, I have declared a public property called someData:
properties (Access = public)
someData = '';
From within the GUI app, testFun is called with app as a function argument:
testFun is defined as follows:
inputData.someData = 'hello world';
As you can see, there are no output arguments defined in testFun.
Yet when I run the app like this, the someData property gets the value 'hello world'.
How can this behavior be explained?