What is the best way to manage the order in which Angular validators are evaluated?

Currently working with Angular 1.5

I have a good grasp on how angular validators are added to a field when the directive is triggered, and then all the validators fire when the control's value changes. For an amount field, I have implemented three different validations (correct characters, maximum length, and cannot be zero). In this case, I don't need to check for non-zero values if the field doesn't meet the valid amount criteria. Instead of re-checking all the valid amount conditions, I am interested in confirming if control.$validator.amountFormat. is met first.

Is there any way to ensure that the custom format validator I created runs before the greater than zero validator? There are various other scenarios like this.

This is my current implementation:

ctrl.$validators.amountFormat = (modelValue: string, viewValue: string) => {
    if (ctrl.$isEmpty(viewValue)) {
        return true;
    }

    return isAmount(viewValue);
}

ctrl.$validators.amountGreaterThanZero = (modelValue: string, viewValue: string) => {
    if (!isAmount(viewValue)) {  
        return true;
    }

    return parseFloat(viewValue) > 0;
}

This is my desired setup:

ctrl.$validators.amountGreaterThanZero = (modelValue: string, viewValue: string) => {
    if (ctrl.$error.amountFormat) {
        return true;
    }

    return parseFloat(viewValue) > 0;
}

Answer №1

If you're curious about the sequence in which $validators are triggered after successful completion of $parsers, check out this informative link in the

Discovering the $validators pipeline
section:

In my approach, I crafted a parser that accomplishes this: if the user inputs a valid amount, it gets stored in modelValue; otherwise, modelValue remains empty.

ctrl.$parsers.push((viewValue: string) => {
    var modelReturnValue = '';

    if (ctrl.$isEmpty(viewValue)) { return modelReturnValue; }

    if (this.isAmount(viewValue)) {
        modelReturnValue = viewValue;
    }

    return modelReturnValue;
});

Consequently, in my validators, I utilize modelValue instead of viewValue.

ctrl.$validators.amountFormat = (modelValue: string, viewValue: string) => {
    if (ctrl.$isEmpty(viewValue)) {
        return true;
    }

    // The format validator must validate the viewValue to avoid showing a format error when nothing is typed
    return isAmount(viewValue);
}

As an alternative, the amountFormat validator could simply verify if viewValue != modelValue since we store a valid amount as the modelValue.

ctrl.$validators.amountGreaterThanZero = (modelValue: string) => {
    // Since we return an empty string for invalid amounts, we can assume that the modelValue will be empty
    if (ctrl.$isEmpty(modelValue)) {  
        return true;
    }

    return parseFloat(modelValue) > 0;
}

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