how a matlab .m code can write text in a GUI textarea?

Let's suppose a simple file "test.m" with the following code:

obj = app1;

for i = 1:10
    fprintf('\ni = %d\n', i);
    if i==1
        str = num2str(i);
    else
        str = sprintf('%s\n%s', str, num2str(i));
    end
    obj.writeText('1', str);       % line 10
    obj.TextArea_2.Value = str;    % line 11
end

"app1.mlapp" is a GUI class made through appdesigner. In its code I defined two textareas:

% Create TextArea_1
  app.TextArea_1 = uitextarea(app.UIFigure);
  app.TextArea_1.Position = [47 187 259 150];

% Create TextArea_2
  app.TextArea_2 = uitextarea(app.UIFigure);
  app.TextArea_2.Position = [335 187 259 150];

and defined a public function:

methods (Access = public)
    function writeText(app, ind, text)
        if ind <= length(2)
            ta = ['TextArea_', ind];
            ta.Value = text;
        end
    end
end

only line 11 prints in in TextArea_2. So, why doesn't line 10 print in TextArea_1 ???

thanks in advance.

PS: in the attached file "GUI-example.zip", it's included the 2 files "app1.mlapp" and "test.m".

[Otavio Carpinteiro]

even if using "eval", such as:

function writeText(app, ind, text)
    cmd = sprintf('TextArea_%s.Value = ''%s'';', ind, text);
    eval(cmd);
end

it doesn't work ...

[Otavio Carpinteiro]

the matlab message is:

>> test
i = 1
i = 2
Error using app1/writeText (line 21)
Error: Character vector is not terminated properly.

Error in test (line 10)
    obj.writeText('1', str); 

inexplicable ...

[Stephen23]

Putting pseudo-indices into variable names is a sign that you are doing something wrong.

Create one handle array:

app.TextArea(1) = uitextarea(app.UIFigure);
app.TextArea(2) = uitextarea(app.UIFigure);

and then use basic, simple, efficient indexing to access them, or even set / get for multiple objects/properties at once.

[Otavio Carpinteiro]

> Putting pseudo-indices into variable names is a sign that you are doing something wrong.

certainly, but there was no other way. Handles are for functions, and what it's needed is to atribute one value to a variable "TextArea_X.Value", where X = 1, 2, ...

surely I can create a cell array of function handles, and call any function through its corresponding index of the cell array. Each function "func_X" changes the value of the variable "TextArea_X.Value". As my GUI should have around 50 textarea components, it would have 50 functions, one to write to its corresponding textarea component. Another possibility is to have just one function with a switch containing 50 clauses.

as this is the first time I program in matlab, I was expecting there would be a better way. Unfortunately, it seems there is not.

thank you for your reply. I'm closing this request ...

Answer 1

[Otavio Carpinteiro]

I'm closing this request, thanks.

Answer 2

[Walter Roberson]

length(2) is 1 and '1' < 1 is false, so you never execute the lines

            ta = ['TextArea_', ind];
            ta.Value = text;

If you did, then you get an error message, because ta would contain a character vector, and character vectors do not have a Value fieldname or property or method.

You should not be doing what you are trying to do. http://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

You should make app.Text_Area a vector that you index into.

[Otavio Carpinteiro]

thanks for your reply. Indeed, eval is not a good solution. I guess making "app.TextArea" a vector will not solve the problem because the name of the textarea is "TextArea_1" and so, "TextArea_1.Value" would not be the same as "TextArea(1).Value". I think I tried to create the textarea using "TextArea(idx)" before by modifying the code generated by appdesigner. But I'll try it tomorrow. Thanks.

[Walter Roberson]

You can have the app designer generate TextArea_1 and TextArea_2 for you, but your initialization can also do

app.TextArea = [app.TextArea_1, app.TextArea_2];

after which you can index app.TextArea(idx).Value

[Otavio Carpinteiro]

as an array:

>> app.TextArea = [app.TextArea_1, app.TextArea_2]
Unable to resolve the name app.TextArea_1.

as a cell array:

>> app.TextArea = {app.TextArea_1, app.TextArea_2}
Unable to resolve the name app.TextArea_1.

as I reply to Stephen Cobeldick, I have two ways to workaround. I'll choose one of them.

thank you for your reply. I'm closing this request ...