App Designer app property is saved as double although I enter strings

Question

Tim Koopman 2020-2-8

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/504416-app-designer-app-property-is-saved-as-double-although-i-enter-strings

编辑： Adam Danz 2021-8-31

In App Designer I run into the issue of not being able to assign a string (or any other variable type) other than double to new properties I create.

This is my code (simplified):

properties (Access = public)
        nameSave 
end
        
        
% Button pushed function: Calculate
function CalculateButtonPushed(app, event)
app.nameSave(1,1) = "John"
app.nameSave(1,2) = "Peter"
end

I would now assume that nameSave is a 1x2 string array just like how it works in the normal editor. However, in App Designer, nameSave is a 1x2 double filled with [NaN,NaN] although I obviously assign strings to nameSave.

What is the mistake I am making?

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Answer 1

Adam Danz 2020-2-8

2
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/504416-app-designer-app-property-is-saved-as-double-although-i-enter-strings#answer_414525

编辑：Adam Danz 2020-2-8

在 MATLAB Online 中打开

By default the property is initially defined to class=double.

Here are two solutions.

Set the property to a string array by placing the word string next to the property definition.

properties (Access = private)
nameSave    string

Don't use indexing on the first assignment

app.nameSave = "John";  %now it's a string array!
app.nameSave(2) = "Mary"; 

If needed, you can use the following to determine whether nameSave is emtpy: isempty(app.nameSave)

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hzh 2021-8-31

properties (Access = private)

nameSave string

This is really the worst syntax I have ever seen in my life. Took me an hour to figure out how to properly declare the property to be a string array. Very counterintuitive.

properties (Access = private)

nameSave = ""

should have been the one used

Adam Danz 2021-8-31

编辑：Adam Danz 2021-8-31

> This is really the worst syntax I have ever seen in my life

I doubt it, but I feel your frustration.

> Took me an hour to figure out how to properly declare the property to be a string array

I'm sorry this answer didn't perfectly address whatever you were looking for and that you had to invest some of your own valuable time to figure out a solution that makes sense to you.

I took some time to find this page below so you can get more familiar with the available syntaxes for declaring properties.

https://www.mathworks.com/help/matlab/matlab_oop/specifying-properties.html

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