Custom Error Messages¶

Let’s take a look at how you would use the addUnmetCondition to create custom error messages and what behaviours would typically go with it.

It is important to remember that the addUnmetCondition function only provides an error message but it does not stop anything from being calculated. How the calculator reacts is up to the calculatorian to decide.

Theoretically the sky is the limit, you can get cwazy and implement anything you’d like, but in reality you will be doing the same thing we always do: hide the conflicting variables.

See also

We have created a calculator using this code so that you can see the results for yourself. Check it out at Error Message on BB

Let’s take a look at an example of how to do this and then go over the key points.

'use strict';

omni.onResult(['b'], function(ctx) {
    ctx.hideVariables('c');

    if (!ctx.getNumberValue('b')) {
        ctx.addUnmetCondition("Division by zero is mathematica 'undefined'");
        ctx.addUnmetCondition("Value of " + ctx.getLabel('c') +
                              " is " + ctx.getNumberValue('c') +
                              " which is not a valid result."
                             );
    } else {
        ctx.showVariables('c');
    }
});

The equation present in the calculator is c = a/b, so we’re basically checking that b is not zero. Our onResult function will only be triggered once b has a value.

Tip

We have used the value of a variable as a boolean again. Our condition 1 !b is the same as b == 0 but looks more elegant and readable.

The function addUnmetCondition takes any string input so we can take advantage of that to make customized error messages that help the user understand better where the mistake was made and correct it. The second message is not standard procedure, is only there to exemplify that there can be more than one error message on the same condition and how you can create dynamic text in them.