Increment Item Value

[Hemingway]

I am so curious, is that possible to simple increment item value via builded write-item function in widget behaviour attributes? something like this:

My notation of course not working. Or I have to create my own UI-Action? 

[webiq-sk · Accepted solution]

Write-item does exactly one thing: write the specified item to the absolute input in the value field - there's no magic parsing happening here so it will not work as you expected. This is true for all fields in WebIQ Designer - nowhere can you do any calculations.

You can however create a custom UI action to achieve this. Please note that this example requires at least WebIQ 2.15.7 - with previous versions you'd have to subscribe to the item just to get the item properties (min/max) and then unsubscribe again.

/**
 * Custom UI-Action 'increment-item-value'.
 *
 * Description:
 * [Add description here]
 */
(function() {
    var actions = shmi.pkg("visuals.session.userActions"); //get reference to userActions object

    /**
     * UI-Action 'increment-item-value' implementation
     *
     * @params {any[]} parameters  configured ui-action parameters
     * ---- Initial parameters, needs to be updated manually when changed ----
     * @param {string} parameters[0]  Item
     *
     */
    actions["increment-item-value"] = function(parameters) {

        const itemName = parameters[0],
            im = shmi.visuals.session.ItemManager;

        // Read item value
        im.readDirect([itemName], function(err, result) {
            if (!err) {
                let itmData = {};

                // Read min/max
                im.getItemProperties([itemName], (err, properties) => {
                    if (!err) {
                        const max = properties[itemName].max; // min would be for minimum
                        const newValue = result[itemName] + 1;
                        if (newValue > max) {
                            console.log("Not updating item value, because it would exceed the maximum value of " + max);
                        } else {
                            // Write item value
                            itmData[itemName] = result[itemName] + 1;
                            im.writeDirect(itmData, function(err, result) {
                                if (!err) {
                                    console.log('Increased item value to ' + itmData[itemName]);
                                } else {
                                    shmi.notify("Couldn't write item: " + itemName, 'ERROR');
                                }
                            });
                        }
                    } else {
                        shmi.notify("Couldn't read item properties: " + itemName, 'ERROR');
                    }
                });
            } else {
                shmi.notify("Couldn't read item: " + itemName, 'ERROR');
            }
        });
    };
}());