Hi guys, I'm trying to create a multiwindow app. It's my first app but I'm taking this error. How can I solve it?

[Adam Danz]

Copy-pasted code is much better to work with than an image of code.

[Adam Danz]

What are the values of app.a, app.b etc. and where do they come from? Somewhere the string "mainApp" is being passed to DialogApp() and the string should be "MainApp" instead.

[ahmet emin arslan]

 % Properties that correspond to app components
    properties (Access = public)
        UIFigure              matlab.ui.Figure
        ResultEditFieldLabel  matlab.ui.control.Label
        Result                matlab.ui.control.NumericEditField
        Button                matlab.ui.control.StateButton
    end

    
    properties (Access = private)
        DialogApp   % Dialog box app
        a = 0;      % a value
        b = 0;      % b value
        c = 0;      % c value
    end
    
    methods (Access = public)
        
        function result = calculate_product(app, a, b, c)
            % Store inputs as properties
            app.a = a;
            app.b = b;
            app.c = c;
            % Calculate the product
            result = (app.a*app.b)^app.c;
            
            % Change the result field value
            app.Result.Value = result;
            
            % Re-enable the button
            app.Button.Enable = 'on';

            
        end
    end
    

    % Callbacks that handle component events
    methods (Access = private)

        % Code that executes after component creation
        function startupFcn(app)
            % Call calculate_product function to display an initial value
            calculate_product(app, app.a, app.b, app.c)
            
            app.Result.Value = 0;

        end

        % Value changed function: Button
        function ButtonPushed(app, event)
            % Disable button while dialog is open
            app.Button.Enable = 'off';
            
            % Open the dialog box and pass inputs
            app.DialogApp = DialogApp(app, app.a, app.b, app.c);

            
        end

        % Close request function: UIFigure
        function UIFigureCloseRequest(app, event)
           % Delete both apps
            delete(app.InputApp)
            delete(app)

        end
    end

    % Component initialization
    methods (Access = private)

        % Create UIFigure and components
        function createComponents(app)

            % Create UIFigure and hide until all components are created
            app.UIFigure = uifigure('Visible', 'off');
            app.UIFigure.Position = [100 100 258 361];
            app.UIFigure.Name = 'UI Figure';
            app.UIFigure.CloseRequestFcn = createCallbackFcn(app, @UIFigureCloseRequest, true);

            % Create ResultEditFieldLabel
            app.ResultEditFieldLabel = uilabel(app.UIFigure);
            app.ResultEditFieldLabel.HorizontalAlignment = 'right';
            app.ResultEditFieldLabel.Position = [61 271 39 22];
            app.ResultEditFieldLabel.Text = 'Result';

            % Create Result
            app.Result = uieditfield(app.UIFigure, 'numeric');
            app.Result.Position = [115 271 100 22];

            % Create Button
            app.Button = uibutton(app.UIFigure, 'state');
            app.Button.ValueChangedFcn = createCallbackFcn(app, @ButtonPushed, true);
            app.Button.Text = 'Inputs';
            app.Button.Position = [99 230 100 22];

            % Show the figure after all components are created
            app.UIFigure.Visible = 'on';
        end
    end

    % App creation and deletion
    methods (Access = public)

        % Construct app
        function app = MainApp

            % Create UIFigure and components
            createComponents(app)

            % Register the app with App Designer
            registerApp(app, app.UIFigure)

            % Execute the startup function
            runStartupFcn(app, @startupFcn)

            if nargout == 0
                clear app
            end
        end

        % Code that executes before app deletion
        function delete(app)

            % Delete UIFigure when app is deleted
            delete(app.UIFigure)
        end
        end
        
        that is first app
        
        classdef DialogApp < matlab.apps.AppBase

    % Properties that correspond to app components
    properties (Access = public)
        UIFigure         matlab.ui.Figure
        aEditFieldLabel  matlab.ui.control.Label
        A                matlab.ui.control.NumericEditField
        bEditFieldLabel  matlab.ui.control.Label
        B                matlab.ui.control.NumericEditField
        cEditFieldLabel  matlab.ui.control.Label
        C                matlab.ui.control.NumericEditField
        CalculateButton  matlab.ui.control.StateButton
    end

    
    properties (Access = private)
        CallingApp      % Main app object
    end
    

    % Callbacks that handle component events
    methods (Access = private)

        % Code that executes after component creation
        function startupFcn(app, MainApp, a, b, c)
            % Store main app in property for CloseRequestFcn to use
            app.CallingApp = mainApp;
            
            % Update UI with input values
            app.A.Value = a;
            app.B.Value = b;
            app.C.Value = c;
        end

        % Value changed function: CalculateButton
        function CalculateButtonPushed(app, event)
            % Call main app's public function
            calculate_product(app.CallingApp, app.A.Value, app.B.Value, app.C.Value)
            
            % Delete the dialog box
            delete(app)

            
        end

        % Close request function: UIFigure
        function UIFigureCloseRequest(app, event)
            % Enable the button in main app
            app.CallingApp.Button.Enable = 'on';
            
            % Delete the dialog box 
            delete(app)

            
        end
    end

    % Component initialization
    methods (Access = private)

        % Create UIFigure and components
        function createComponents(app)

            % Create UIFigure and hide until all components are created
            app.UIFigure = uifigure('Visible', 'off');
            app.UIFigure.Position = [100 100 218 321];
            app.UIFigure.Name = 'UI Figure';
            app.UIFigure.CloseRequestFcn = createCallbackFcn(app, @UIFigureCloseRequest, true);

            % Create aEditFieldLabel
            app.aEditFieldLabel = uilabel(app.UIFigure);
            app.aEditFieldLabel.HorizontalAlignment = 'right';
            app.aEditFieldLabel.Position = [81 262 25 22];
            app.aEditFieldLabel.Text = 'a';

            % Create A
            app.A = uieditfield(app.UIFigure, 'numeric');
            app.A.Position = [121 262 47 22];

            % Create bEditFieldLabel
            app.bEditFieldLabel = uilabel(app.UIFigure);
            app.bEditFieldLabel.HorizontalAlignment = 'right';
            app.bEditFieldLabel.Position = [81 230 25 22];
            app.bEditFieldLabel.Text = 'b';

            % Create B
            app.B = uieditfield(app.UIFigure, 'numeric');
            app.B.Position = [121 230 47 22];

            % Create cEditFieldLabel
            app.cEditFieldLabel = uilabel(app.UIFigure);
            app.cEditFieldLabel.HorizontalAlignment = 'right';
            app.cEditFieldLabel.Position = [81 194 25 22];
            app.cEditFieldLabel.Text = 'c';

            % Create C
            app.C = uieditfield(app.UIFigure, 'numeric');
            app.C.Position = [121 194 47 22];

            % Create CalculateButton
            app.CalculateButton = uibutton(app.UIFigure, 'state');
            app.CalculateButton.ValueChangedFcn = createCallbackFcn(app, @CalculateButtonPushed, true);
            app.CalculateButton.Text = 'Calculate';
            app.CalculateButton.Position = [75 126 100 22];

            % Show the figure after all components are created
            app.UIFigure.Visible = 'on';
        end
    end

    % App creation and deletion
    methods (Access = public)

        % Construct app
        function app = DialogApp(varargin)

            % Create UIFigure and components
            createComponents(app)

            % Register the app with App Designer
            registerApp(app, app.UIFigure)

            % Execute the startup function
            runStartupFcn(app, @(app)startupFcn(app, varargin{:}))

            if nargout == 0
                clear app
            end
        end

        % Code that executes before app deletion
        function delete(app)

            % Delete UIFigure when app is deleted
            delete(app.UIFigure)
        end
    end
    
    that is second app

Answer 1

[Adam Danz]

I beleive your error is here

% Code that executes after component creation
        function startupFcn(app, MainApp, a, b, c)
            % Store main app in property for CloseRequestFcn to use
            app.CallingApp = mainApp;    % <----------------------------- HERE

Should be

            app.CallingApp = MainApp;   % with capital M

Make that change, save the app, close the app, restart it, and test it. If the problem persists, I'd be glad to look further.

[ahmet emin arslan]

App is working :))

[Adam Danz]

Nice! Glad I could help!