Why custom validator is used

The CustomValidator control can work client-side, server-side, or both. Custom validation on the client Client-side validation provides immediate feedback, if error occurs. Step 2: Create Javascript function. The second parameter arguments is an object that supports a property called Value; it represents the value of the form field, which is validated by your client-side function.

The Directive reuses the required function from the static Validators class. Instead of implementing a standalone validation function, we are going to add it as a static field inside a ColorValdiator class. We added other validation functions called red and white.

Those color functions are not configurable and therefore directly return a error object or null. Under the hood those functions call a generic color function that verifies the value of a control against the passed color name. Notice that this function is configurable and therefore callable. This refactoring allows us to use Intellisense and access the blue validator over ColorValidators. Furthermore we know that our validation function is not configurable and therefore we don't need to call it.

Currently, our grouped validator can not yet be used in template-driven forms. We need to provide a directive and then call ColorValidators inside of it. By refactoring and restructuring our code a bit we improved the developer experience of our custom validators without loosing any features. In the end, a custom validator is just a function that returns either an error object or null. If a validator is customizable, it needs to be wrapped with a function.

Most tutorials teach you to implement a validator as a factory function which is totally valid. However, the usage is not as nice as the built-in validators from Angular.

We have no Intellisense, and if you don't follow a certain convention its not clear if a Validator needs to be called or not.

By reverse-engineering the Angular source code on validators we found an approach that shows us how to group validators. Implementing the validators as static class fields instead of standalone functions allows us to group our Validators and improve Intellisense.

Furthermore, we can follow the "callable if configurable" convention. With this small refacoring we can improve developer experience. Maintainer of multiple open source projects. Always eager to learn, share, and expand knowledge. The second part of how we organized the system of settings for all textfields in Taiga UI with the power of Dependency Injection in Angular. Pearson automatically collects log data to help ensure the delivery, availability and security of this site. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

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This privacy statement applies solely to information collected by this web site. Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information. We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. It turns out the problem was the name of the javascript function was the same as the server control ID. Did you verify that the control causing the post back has CausesValidation set to tru and that it does not have a validation group assigned to it?

Also check that you are not using validation groups as that validation wouldnt fire if the validationgroup property was set and not explicitly called via. Server-side validation won't fire if client-side validation is invalid, the postback is not send. What I was trying to do in my code was to only ensure that some text field A has some text in the field when text field B has a particular value. Otherwise, A can be blank or whatever else.

Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Asked 12 years, 7 months ago. Active 6 years, 11 months ago. Viewed k times. I looked at the output and ASP. Edit: Typo I pasted in the wrong function, problem still the same Just another update to the last comment: where by the TextBox cannot be empty.

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