Join Justin Schwartzenberger for an in-depth discussion in this video Validation: custom, part of Angular 2 Essential Training.
- [Instructor] Let's build a custom validator.…To build your own custom validators…you need to create a function that will receive an object…which Angular will pass in as either…a FormControl, FormGroup, or FormArray…and that function needs to return null when valid…and return an object if invalid.…So, let's build a year validator for the year field,…which is a FormControl.…In the media-item-form.component.ts file,…we can create a method named yearValidator…and give it a parameter named control.…
We want the year field to be optional,…so the first bit of logic we will add…is to check if the value's empty,…and, if so, return null,…telling the control that the field is valid.…If it makes it past that,…we want to convert the value, which is a string,…into a number, so we can call parseInt on control.value…and capture it into a local variable…and then we will set up a min and max year.…Let's assume that 1900 to 2100 is the time frame…that media will have its run and then…we'll be all onto other things like VR or something.…
Justin Schwartzenberger steps through the framework one feature at a time, focusing on the new component-based architecture of Angular 2. You'll learn what Angular is and what it can do, as Justin builds a full-featured web app from start to finish. After mastering the essentials, you can tackle the other project-based courses in our library and create your own Angular app.
- What is Angular?
- Setting up an Angular template
- Creating a component
- Binding events and properties
- Getting data to components
- Using directives and pipes
- Creating Angular forms
- Validating form data
- Understanding dependency injection
- Providing services
- Making HTTP calls
Skill Level Intermediate
1. Architecture Overview
3. Directives and Pipes
5. Dependency Injection and Services
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