Validate Settings Using Functions

You can impose specific restrictions on settings values by specifying a validation function for a setting or group. A validation function accepts a potential setting value as an argument, and throws an error if the value does not meet a specific requirement.

MATLAB^® defines several validation functions.

To specify a validation function when creating a factory setting, use the 'ValidationFcn' name-value pair argument and specify the function handle. For example, add the setting MyLogicalSetting to the myfactorysettings group and specify that its value must be a logical scalar.

addSetting(s.myfactorysettings,'MyLogicalSetting','ValidationFcn', ...
    @matlab.settings.mustBeLogicalScalar);

Try setting the value of MyLogicalSetting to a nonlogical value. As expected, MATLAB throws an error.

s.myfactorysettings.MyLogicalSetting.PersonalValue = 10

Error setting "MyLogicalSetting" in group "myfactorysettings":
Value must be logical or convertible to logical.

You also can specify a validation function for an entire factory settings group. When specified, the function is used to validate the values of all factory settings within the group that do not specify their own validation functions. This includes settings in subgroups, as long as the subgroup or settings do not specify their own validation functions. For example, create the settings group mylogicalsettings and specify the validation function matlab.settings.mustBeLogicalScalar.

addGroup(s.myfactorysettings,'mylogicalsettings','ValidationFcn', ...
    @matlab.settings.mustBeLogicalScalar);

Create the setting MyLogicalSetting within the mylogicalsettings group and try setting the value of the setting to a nonlogical value. As expected, MATLAB throws an error.

addSetting(s.myfactorysettings.mylogicalsettings,'MyLogicalSetting')
s.myfactorysettings.mylogicalsettings.PersonalValue = 10;

Error setting 'MyLogicalSetting' in group 'mysettings': 
Value must be logical or convertible to logical.

Define Custom Validation Functions

You also can create your own validation functions to check factory settings for properties that are not covered by the MATLAB validation functions. Validation functions are ordinary MATLAB functions that are designed for the purpose of validating the values of settings. They must satisfy these conditions:

Place validation functions on the MATLAB path to make them available.

For example, create a function to validate whether the value of a setting is an even number.

function evenNumberValidationFcn(x)
    errorMsg = 'Value must be an even number.';
    iseven = isnumeric(x) && mod(x, 2) == 0;
    assert(iseven,errorMsg);
end

Add this validation function to a new setting.

addSetting(s.mysettings,'MyEvenNumberSetting','ValidationFcn',@evenNumberValidationFcn);

Set the value of MyEvenNumberSetting to an odd number. As expected, MATLAB throws an error.

s.mysettings.MyEvenNumberSetting.PersonalValue = 1;

Unable to validate settings data. Error using evenNumberValidationFcn (line 4)
Value must be an even number.

You also can create custom validation functions to make use of MATLAB validation functions that require multiple inputs, such as mustBeGreaterThan, mustBeLessThan, mustBeGreaterThanOrEqual, mustBeLessThanOrEqual, and mustBeMember. For example, this function validates that the value of a setting is one of four colors.

function colorValidationFcn(val) 
    mustBeMember(val, ['Black' 'Blue' 'Yellow' 'Green']); 
end

For more information about adding a validation function to a factory setting or factory settings group, see addSetting and addGroup.

Modify the Factory Settings Tree

The factory settings tree creation function creates the settings tree for the latest toolbox version. To update the factory settings tree for the latest toolbox version, modify the factory settings tree creation commands.

For example, suppose that in version 2 of mytoolbox, you want to rename the settings MyFontSize and MyFontColor to FontSize and FontColor. Change the settings names in createMyToolboxFactoryTree.mlx.

function myToolboxFactoryTree = createMyToolboxFactoryTree()
    myToolboxFactoryTree = matlab.settings.FactoryGroup.createToolboxGroup('mytoolbox', ...
        'Hidden',false);

    toolboxFontGroup = addGroup(myToolboxFactoryTree,'font','Hidden',false)
    addSetting(toolboxFontGroup,'FontSize','FactoryValue',11,'Hidden',false, ...
        'ValidationFcn',@matlab.settings.mustBeNumericScalar)    
    addSetting(toolboxFontGroup,'FontColor','FactoryValue','Black', ...
        'Hidden',false,'ValidationFcn',@matlab.settings.mustBeStringScalar);
end

Log Changes to the Tree

Create a function with no inputs to store the instructions for upgrading the personal settings from a previous version of the toolbox. Include the file with your toolbox code when you package and distribute the toolbox. Recording changes to the factory settings tree ensures that toolbox users upgrading to a new version do not have backward incompatibility issues with their existing toolbox settings. Modifications that can cause backward incompatibility issues include renaming, moving, and removing toolbox factory settings or settings group. You do not need to record the addition of new settings to the factory settings tree.

In the function, add a settings file upgrader object for each version of the toolbox that contains changes to the factory settings tree. Use the move and remove functions to record individual changes. For example, the function createMyToolboxSettingsFileUpgraders.mlx records the changes to MyFontSize and MyFontColor for version 2 of mytoolbox.

function upgraders = createMyToolboxSettingsFileUpgraders()
    upgraders = matlab.settings.SettingsFileUpgrader('Version2');
    move(upgraders,"mytoolbox.font.MyFontSize","mytoolbox.font.FontSize");
    move(upgraders,"mytoolbox.font.MyFontColor","mytoolbox.font.FontColor"); 

end

Do not modify recorded upgrade instructions in the settings tree upgrade function after packaging and distributing the toolbox to your users. Modifying instructions can have unexpected results. If you make additional changes to the settings tree, record the changes by appending them to the existing instructions, or by creating a new upgrader instance.

For example, this code records changes for version 2 and version 3 of mytoolbox.

function upgraders = createMyToolboxSettingsFileUpgraders()
    upgraders = matlab.settings.SettingsFileUpgrader('Version2');
    move(upgraders,"mytoolbox.font.MyFontSize","mytoolbox.font.FontSize");
    move(upgraders,"mytoolbox.font.MyFontColor","mytoolbox.font.FontColor"); 

    upgraders(2) = matlab.settings.SettingsFileUpgrader('Version3');
    remove(upgraders(2),"mytoolbox.font.FontName"); 
end

Modify the Factory Settings JSON File

In order for MATLAB to know what function to use to upgrade the toolbox factory settings tree, specify the settings tree upgrade function in the factory settings file (settingsInfo.json). For example, in settingsInfo.json for mytoolbox, specify createMyToolboxSettingsFileUpgrader as the settings tree upgrade function.

{
"ToolboxGroupName" : "mytoolbox",
"Hidden" : false,
"CreateTreeFcn" : "createMyToolboxFactoryTree",
"CreateUpgradersFcn" : "createMyToolboxSettingsFileUpgraders"
}

Include the files createMyToolboxFactoryTree.mlx, createMyToolboxSettingsFileUpgraders.mlx, and settingsInfo.json when you package and distribute mytoolbox. Place the settingsInfo.json in the toolbox resources folder.

Examine Personal Settings Tree Upgrade Results

After upgrading the personal settings of a toolbox, you can examine the results to ensure that the upgrade occurred correctly. To examine the upgrade results, use the matlab.settings.loadSettingsCompatibilityResults function.

To ensure the upgrade occurs correctly, examine the upgrade results before distributing the toolbox. For example, examine the upgrade results for version 2 of mytoolbox before distributing the toolbox.

You also can examine upgrade results after you have installed a new version of a toolbox. This approach is useful, for example, if you are helping a toolbox user troubleshoot their toolbox settings after an upgrade.

For example, suppose that you have version 1 of mytoolbox installed and have set personal values for several settings. After installing version 2 of mytoolbox, examine the upgrade results to ensure that your personal settings moved over correctly.