Ans. Fabio has grown an experience commnunity manager. Let's create a CustomerForm that will include our AddressForm amongst other controls: As you can see we are able to add nesting to our forms very easily with this approach. The resulting paper you are going to read is based on Fabio Biondis talk. To solve that, angular provides a service called FormBuilder. So we could pass addressLine1 an initial value like new FormControl('123 Main Street') and when the page loads that value will pre-populate in the addressLine1 field with the street name of the 123 Main Street. The beautiful thing about validations in Angular is that they can be anything that returns a ValidatorFn. His hobbies include travelling, programming, and watching sitcoms. In this tutorial we are going to take a close look at one of the two ways to create forms in angular. That is better, but our form is still saving on every keystroke when it is in a valid state. These will be used to handle asynchronous validations that might come from an api or some other service that can't be run synchronously. Template-driven forms use the existing form tag to create the forms. When your forms grow in complexity, you can split it in FormGroup or split the UI in Components. The problem with this solution is that ngSwitch can grow. VIDEO SERIES FOR MANAGERS AND PRODUCT OWNERS. This class has three main methods group, control, and array. Each change to the form state returns a new state, which maintains the integrity of the model between changes. We have a function setup below-. Let's take a look at what our template would look like if we were using Angular Material: As you can see, all we need to do to tie our AddressForm into the DOM inputs themselves is to pass it the FormControl using the formControl directive. The structure of the JSON can contain properties such as label, type (of the input), validators, etc. But please wait with that, until you read this article and fully understand the topic. Instead we have to create a different one. This is why we need to create a copy of the data. To use the FormBuilder, we need to request it via dependency injection. For more details and explanations, you can refer to the KnowledgeHut angular online training guide to get help from our experts to help you develop interactive angular reactive forms. 
You need to use the same template for both FormBuilder and FormControl classes available. If the user decides to abort his action, we can not recover the previous state, as we have overwritten it. Also, I typically create a new folder called models to contain all models of the application. Ans. The various features available in this FormGroup control can be merged into a separate function that provides different API functions. To see the result, I've also added a paragraph to print out our form-model as json. No, the reactive forms angular are immutable. Template-driven forms are driven by code in the template. Though this form, as-is, is not very complex let's take a step back and look at this form from a high architectural level. Just use the following command of the angular-cli: This will create a basic component for us to use. This type of overwriting everything is called "immutable objects". Template-Driven Forms represent the first approach we learn as developers, and often it is the only one we use inside our applications. You can just replace you previous code if you want to. Both of these approaches process and manage your form data differently and therefore both have their own unique tradeoffs. Here is a quick summary of everything we covered: - What are Angular Reactive Forms and Template-Driven Forms. Every form group can have a second parameter where you can specify a custom validator for the form group itself. Its structure is defined inside the Component class instead of the Template file definition: RxJS is a library with a clear API to work with both asynchronous and synchronous code thanks to pipeline operators and the usage of the Observable concept. Therefore, we don't need to add conditional logic in our templates (making them reusable) and we put that responsibility solely in the Form class (supporting SRP). A user could submit anything (or nothing) into this form regardless of its validity. If your form is valid, you can add the submit button, and if not, then disable the submit button. Now let's take our above AddressForm and create it using FormBuilder: You will quickly notice that there isn't much magic happening here other than helper methods for making form creation less verbose. The syntax is very much like that of the HTML Forms, and this gives us a good reason to prefer it. Thanks to the power of Reactive forms, you can add nesting to our forms as deep as you need to. This is an affiliate link. This is true for reactive forms, as well. Instead of defining the form in your template, the structure of the form is defined in code. which results in an empty object, or pass a set of default parameters along: All in all the revert method simply looks like this: In this tutorial we learned how to create forms with angular using the reactive-forms method. We now have a form that auto-saves in just a few lines of code! In both cases, we are no longer allowing users to submit when the form is invalid. To define our form-model, we create a new FormGroup. Let's now consume this reusable component in our original Component: To finish up this refactor let's now create a reusable dropdown component: Because we already did the work for the shared-ui-error making this dropdown component was super simple. The first step in building up reactive forms in Angular is to add the reactive forms module. Bind both the HTML form and the form model together. It is a collection of form controls available in the reactive forms in angular. In this deep dive of Angular Reactive Forms we covered a lot of material! Every control in the form (select, input, checkbox, etc.) From the example of our TypeScript code above, we can say that the code is starting to look cluttered already. The module can be imported within the component class to use its functionalities. Thankfully, because Reactive forms are reactive, we can leverage the valueChanges observable stream to handle this fairly easily: I told you that would be easy! Instead of defining our form-model inline, the FormBuilder allows us to pass in any JavaScript object. We now have completely de-coupled our form from the component and made the template completely reusable. This provides us great flexibility and maintainability as our application grows. The controls are then added using the Ngmodule and can be grouped. Now let's add a filter to only save when the form is valid. Therefore, a form is treated like a stream of data where every field acts like an Observable. This prevents the user from ever being able to click submit when the form is in an invalid state. The constructor of this class then takes an object, that can contain sub-form-groups and FormControls. It is a complete process with various steps. Working examples are included. We are altering the original data directly. For each control you can create a component. It acts like a bidirectional data binding. This is useful when you dont know how many controls will be hosted inside your dynamic forms. Though this code works, there are currently no guard rails around submission. After creating the angular reactive forms, it's now time to implement and use the reactive forms in Angular. We will use this class to identify the validation error in a mail and then display it further. A Nested Form Group is a group of input elements that you need to validate together. There are two basic ways to handle this problem. Check the web application development course to get more detailed knowledge of web development and be an advanced web developer. The form model uses different form controls such as FormGroup, FormControl, and FormArrays. It would help if you created a Form control class object whose constructor takes in 3 different parameters, which are-. They are code-driven and are easy to use as compared to template-driven forms. In essence, Reactive forms provide easier and more predictable access to form state because they are built around observable streams. The reactive forms. Here's a code snippet for how to import the ReactiveFormsModule. This maybe sounds a little bit odd now. Lets look at an example of a Reactive Form: As you can see, there is a property being declared as FormControl. Reactive forms are built around observable streams, where form inputs and values are provided as streams of input values, which can be accessed synchronously." Before we start creating our form, we first need to define, which information we would like to gather with it. Usually, behind a succesful group there is a good community leader. You can initialise it with an arbitrary value and link it to the input form from the template. We save your email address, your name and your profile picture on our servers when you sing in. From there it can call a service, dispatch an action, or whatever you need to do to handle the form submission. He is also a professional blogger and writes extensively on skill development. Reactive forms are a form of dynamic form validation, where inputs and values are provided as streams of input values that can be accessed synchronously. Then you can use FormGroup to easily build your forms. No matter the problem you're solving, or the solution you're providing, you will inevitably need to collect form data. The component is responsible for building out the form which is fine for our basic example but what if we need to use this address somewhere else? Inside of that callback, we can access the form's values by its values property. To use this class, you must refactor the login form. We call this mehtod: createFormGroup. The form can provide ease and complexity for the developers to collect and store the data simultaneously. What we do with reactive forms instead, is keeping the data in the form model, until the user hits the submit button. In contrast, the Reactive form is a paradigm. Here is how your component should look like now: For now that is all we need to do code-wise. The approaches are as follows-. In most use cases you will add it to your app's root: Before we begin building our own form, it's a good time to explain the three main types of form components in Angular forms. Here's how you create a FormControl class. Note- The last two parameters are optional and unnecessary to run the class. After importing the classes, your code will look something like this. 
Enough hypothetical talk; let's get our hands dirty and code up an example form using Reactive forms. So let's build out a form that will collect a user's address: This example creates a parent level form or FormGroup that contains individual controls or FormControls for the individual address fields we need to collect from the user. See below: With FormArray we are able to display an element dynamically. So, every FormGroup can be represented with a custom element. Some time ago, during one of the events we hosted at Codemotion Italy, Fabio addressed a hard-felt problem among web application developers. A function for submitting a form will be added to the component class. To answer these questions, let's dive right in and just build a small example using reactive forms together! Once the form is created, the last thing is to add a button to submit the angular reactive forms. Basically, our HTML does look just like a regular form. In fact, I would recommend that you always keep them that similar. Import the Required Modules within the Component. A second common use case for form submission is autosaving. Personally, I've used this technique a lot. Again, we are going to use the reset-button, we have included into our template already. Also, unlike template-driven forms which use directives in the template, the composition, and management of the form is moved out of the template and into the class itself providing the ability for more reusability. You can just pass them an empty string, or fill it with some default-data as I did with the "email"-field. The FormBuilder class has to be imported from @angular/forms: Now we can use that FromBuilder to build our form-model. It is then attached with HTML templates to make it more presentable. Finally, you can generate a form at runtime based on a JSON structure that may come from an XHR REST call. As you can see, I have also added default values to each field, as we will require them later. Next, you need to import all the essential modules such as FormArray, FormGroup, FormControl, etc. Reactive Forms are a source to manage a specific form state at a particular instant of time. The next example is a bit harder, because we introduce FormGroup and FormBuilder to construct our form and to have a better scalability on our forms: Angular provides a service called FormBuilder that allows you to write less code. But, hopefully, it is enough for you to start digging more into it. Reactive forms make it easy to test because you are assured that your data is consistent and predictable. That was what I asked myself and that is what you should ask yourself, too! But we are not done yet. Now let's look at how simple and clean our original component looks: Now that is beautiful! Let's move the AddressForm into its own file that extends FormGroup: How cool is that?!
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