formcontrol angular example


Lets make that come alive, but with no initial data: If we did want to set initial data, we can do so as per the above examples whereby we pre-populate particular strings with information, which typically are data-driven from a backend API. For the email id, we have added the following validation parameters . On submit, the function is called onClickSubmit for which formdata.value is passed. Let us see the how this works in the browser . The base form structure that well be using to implement our reactive form: We have three inputs, the first, the users name, followed by a grouped set of inputs that take the users email address. Let us now consider working on the Template driven form. Now, the email id entered is valid. When we talk about reactive forms (also known as model-driven), well be avoiding directives such as ngModel, required and friends. We have used formdata to initialize the form values; we need to use the same in the form UI app.component.html. Lets refactor our code to use FormBuilder: The refactoring is self-explanatory, but lets roll over it quickly. Which leaves us with a component class that looks like this: Were all done for this tutorial. Directives, simple right?
We have assigned type, name, and placeholder to it. onlinecode Lets assume well bind our FormGroup to a fresh code example before we continue with our signup form, so hopefully things click and you can follow easier: Note: youll notice ngModel and name="" attributes have been toasted, this is good thing as it makes our markup less declarative (which can become complex, quickly, with forms). On clicking submit, the control will pass to the function onClickSubmit, which is defined in the app.component.ts file. On clicking Login, the value will be displayed as shown in the above screenshot. The login is enabled as both the email id and the password are valid. It is given a value that we have used in the app.component.ts file. We make use of cookies to improve our user experience. Let us now try entering the valid email id and see the difference. Let us now try custom validation with the same form. Before digging into these APIs, I would strongly recommend checking out my previous article on template-driven forms to gain a better understanding of whats happening. Email address In the function that we have created, we will check if the length of the characters entered is appropriate. class="error" There is a change which goes in app.module.ts. First up, well need to change our imports from this: To this (with additional constructor injection to make this.fb available as the FormBuilder): This is because user: FormGroup; on our component class is of type FormGroup. Confirm address The ngForm directive needs to be added to the form template that we have created. This is how the values will be seen in the form UI. Confirming email is required Now, for the more internal approach. Oh my. Instead of using FormGroup and FormControl directly, we can use a magical API underneath that does it all for us. You can just add validators or an array of validators required to tell Angular if a particular field is mandatory. Internally, when using required directives in template-driven forms, Angular will actually create this stuff under-the-hood for us, so thats the main difference between the two implementations. Cookies are used to analyze traffic and optimize experience. Before we begin, lets clarify what reactive forms mean from a high level. If the characters are less than five, it will return with the passwd true as shown above - return {"passwd" : true};. On the outside they look simple, but even skilled Angular devs havent grasped every concept in this eBook. Heres the fully working final code from what weve covered for FormGroup and FormControl: Heres the fully working final code from what weve covered for FormBuilder: To learn more techniques, best practices and real-world expert knowledge Id highly recommend checking out my Angular courses - they will guide you through your journey to mastering Angular to the fullest! The structure of these are identical to creating the controls and groups by themselves, its just syntax sugar. The form looks like as shown below. However, we are going to create [disabled] binding just like in the template-driven approach to disable the submit when the form is invalid: All ready to go, now when we actually have validation errors, we need to now show them. Now weve instantiated the FormGroup model, its obviously time to bind it to the DOM. If youre yet to dive into template-driven forms, check out my previous post on it. On the form, we must declare [formGroup] as a binding, and formControlName as a directive with the corresponding Object key name. Were going to explore the absolute fundamentals of the reactive Angular forms, covering FormGroup, FormControl, FormBuilder, submit events, the built-in Validators and error messages. Email is required We have entered only three characters in the password and the login is disabled. Meet FormBuilder! Its actually much easier than youd think. Its just simple sugar, but now you know what its for. In the app.component.html, the submit button is disabled if any of the form inputs are not valid. Thus, if the formdata.valid is not valid, the button will remain disabled and the user will not be able to submit it. In template driven forms, we need to create the model form controls by adding the ngModel directive and the name attribute. We will discuss two ways of working with forms - template driven form and model driven forms.
Angular has built-in validators such as mandatory field, minlength, maxlength, and pattern. In a sense, instead of binding Object models to directives like template-driven forms, we in fact boot up our own instances inside a component class and construct our own JavaScript models. Because this.user is technically our model, we can simply reference the model onSubmit internally, and not pass user through as a function argument: So far, weve implemented zero validation!

Let us now create the function in the app.component.ts and fetch the values entered in the form. *ngIf="user.get('account').get('email').hasError('required') && user.get('account').get('email').touched"> Learn more. This allows us to pull down various pieces of information from our respective method on our component class: Here were using Object destructuring to fetch the value and valid properties from the user reference we pass into onSubmit. This is what weve achieved up until now: This is where things get even smoother! Right now, we have added the required and the pattern matching parameters to take only valid email. "user.get('name').hasError('required') && user.get('name').touched", "user.get('name').hasError('minlength') && user.get('name').touched", "user.get('account').get('email').hasError('required') && user.get('account').get('email').touched", "user.get('account').get('confirm').hasError('required') && user.get('account').get('confirm').touched", ` Now, if we have to read the emailid and passwd, we need to add the ngModel across it. Name is required

The email is displayed at the bottom as we log in. In Angular we create components, which render a template.
Thats it! This is now a replacement for adding to the DOM, which means we never have to touch it. So in app.module.ts, we have imported the FormsModule and the same is added in the imports array as shown in the highlighted code. To enable login, we need more than five characters. Using what weve learned before, lets go ahead: Now our FormGroup and FormControl matches with the DOM structure: Unlike template-driven forms, where we would do something like #f="ngForm", and print f.value in the DOM to check our form out, we do the opposite with reactive forms, as the [formGroup] is a directive that we bind to, passing the public user Object in: This is actually the exact same as the template-driven approach, however we can optionally reference the form internally to the component, instead of passing it in as a value. Full name Instead of using new FormGroup() for example, were injecting FormBuilder as fb, and creating a new this.fb.group().
Tip: use ReactiveFormsModule for reactive forms, and FormsModule for template-driven forms. When it comes to referencing the controls powering the errors, we must use the .controls property on the Object. But first, what does our interface say?

Minimum of 2 characters In the above example, we have created a function password validation and the same is used in a previous section in the formcontrol - passwd: new FormControl("", this.passwordvalidation). Let us now discuss form validation using model driven form. In the model driven form, we need to import the ReactiveFormsModule from @angular/forms and use the same in the imports array. class="error" Please refresh this page to activate it. This is how a code undergoes validation in app.component.ts.

Join 78,277 developers pushing their limits. You can keep it blank in case you want to. Let us enter the data in it and in the submit function, the email id is already entered. Lets say we want to show if there are any errors on the name property of our form: Tip: ?.prop is called the Safe navigation operator. This is what we have: So now weve learned the basis of FormGroup and FormControl, we can think about implementing our own now. Let us now enter a valid length of characters and check. The variable formdata is initialized at the start of the class and the same is initialized with FormGroup as shown above. With Angular 4, we need to import Validators from @angular/forms as shown below . Use an array to contain them. With this, the email id entered is displayed at the bottom. In the above case, the email id entered is invalid, hence the login button is disabled. Lets define what FormControl and FormGroup are: Right, so we have an example of invoking new instances of FormControl and FormGroup, now how do we use them? These are to be accessed using the Validators module. The value is the same reference as printing user.value out in the DOM. In app.component.ts, we need to import a few modules for the model driven form. I always install new Angular projects and forget all the commands I enjoy as a default. Secondly, well be implementing this interface: Before we even dive into reactive forms, we need to tell our @NgModule to use the ReactiveFormsModule from @angular/forms: You will obviously need to wire up all your other dependencies in the correct @NgModule definitions. This is done as follows . *ngIf="user.get('account').get('confirm').hasError('required') && user.get('account').get('confirm').touched"> When you click on the form submit button, the control will come to the above function. If the characters are more than five, it will consider it as valid and the login will be enabled. Let us now try the same on one of the input textboxes, i.e., email id.
The idea is that instead of declaring that we want Angular to power things for us, we can actually use the underlying APIs to do them for us. By using this website, you agree with our Cookies Policy. This has much more power and is extremely productive to work with as it allows us to write expressive code, that is very testable and keeps all logic in the same place, instead of scattering it around different form templates. Thus, wherever we want Angular to access our data from forms, add ngModel to that tag as shown above. Lets begin with a base SignupFormComponent and add our above template: So, this is a typical component base that we need to get going. So, what is FormBuilder?
If you see, we have also added the ngForm to the #userlogin. Thus, we can see the login button is enabled and the user will be able to submit it. In the .html file, we have used formGroup in square bracket for the form; for example, [formGroup]=formdata. Tips and tricks, motivation, courses and exclusive discounts.

For the submit button, we have added disabled in the square bracket, which is given value - !formdata.valid. Its essentially syntax sugar that creates FormGroup, FormControl and FormArray instances for us (well cover FormArray in another article). Let us now see how this is displayed in the browser . The variables emailid and passwd are initialized with default values to be displayed in the form.

We will use both the approaches in the form. Lets fix this. For example, import { FormGroup, FormControl } from '@angular/forms'. Thats literally it, youre free to pass values to your backend API. A newer version of this site just became available. Wrong! So, well need to implement a similar structure with JavaScript Objects using this composition: Yes, we can create nested FormGroup collections!
You can use the built-in form validation or also use the custom validation approach. We also have a .get() method that will lookup that control (I much prefer this as its a nicer API and avoids ?.errors): So, onto implementing the validation, we need to add the following to the correct portions of the form: Tip: The touched property becomes true once the user has blurred the input, which may be a relevant time to show the error if theyve not filled anything out. Well, to begin with, we dont need to actually create any initial data, however, we do need to start understanding FormControl, FormGroup, and finally move onto the amazing FormBuilder. To add validation, we actually need to import the lovely Validators from @angular/forms and pass them in as a second argument to our FormControl instances: Rule: need multiple Validators per FormControl? We have created a simple form with input tags having email id, password and the submit button.
We will create a simple login form and add the email id, password and submit the button in the form. With a template driven form, most of the work is done in the template; and with the model driven form, most of the work is done in the component class. To start with, we need to import to FormsModule from @angular/core which is done in app.module.ts as follows .
We will continue with the same example that we created in one of our previous sections. First, the ngSubmit value-passing: Notice how we just passed user into the onSubmit()? We will now see an example for the same. In this chapter, we will see how forms are used in Angular 4. Agree Keep an eye out for custom validation and more to come. The email id is displayed at the bottom as shown in the above screenshot.