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    Dynamically Render Different Form Input Types with Angular’s Reactive Forms

    Juri StrumpflohnerJuri Strumpflohner

    In this we will generalize our component so that it can take a generic data object which serves as the “API” for dynamically creating our form. We will also see how we can leverage that new structure to render different HTML form input types, such as “text” and “number."

    angularAngular
    ^6.0.0
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    Code

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    Transcript

    Transcript

    Instructor: 00:00 Let's take our dynamically created form object here and make it more usable. As well, we would like to render different kind of input fields, so that I would like to have is something like a type number, which we could use, for instance, for displaying our age property here.

    00:17 Basically, a number field doesn't allow to enter texts, but only numbers and test arrow down and up keys, as well. Let's see how that could work.

    00:25 First of all, let's take here an input property, and we want here an input from the outside, such that our dynamic form component is more reusable. Now let's simply take this object here, which will then be passed from the outside.

    00:41 Let's go to our app component, place it in there, and again connect it with our dynamic form. You also need to make some adjustments here, so basically, that person now is called form data object, and if we save again, we should be fine.

    00:58 In order to render different kind of input fields, we need to expand a little our person object here. We cannot have a single value here, but rather, we have to describe how our first name property of our person looks like.

    01:12 First of all, we will definitely have a value, which will remain just the same. Then we could also add a label which says something like first name, which we could display within our form. Finally, we have the type which defines which kind of input type we are going to render on our HTML.

    01:30 Same thing holds here for our age, but this time, the type will no more be text, but it will be number. Let's simply cut out the other ones.

    01:42 As you can see, our input object here for our form changed, as we have now a sub-object, and no more flat object properties here. Let's jump inside here, and we need to slightly adjust how we process our form data object.

    01:58 First of all, you have to account here for the sub-object, so basically, this one will return as the inner object here. Rather than to accessing it directly, we have to access here the value, which will then now display again the value property on our form.

    02:15 After that, we need to take a look at our person props array and adjust it slightly, as well. Right now, what we push in is the entire object, so we push in basically that inner piece here, which, however, is hard to process within our template.

    02:30 Rather, what we would like to have is something like an array, where the properties are structured as follows. We need basically a label to create the HTML label inside our form.

    02:43 We don't need the value, as it will be bound by the Angular data binding, but we also need the first name property here, which we simply map as a key. That won't be needed in order to properly bind it to our form.

    02:57 This is the end result which we desire to have in our person props here, so let's change this slightly, and basically map it to the property structure which we'll like.

    03:06 The key is simply the property which we are currently processing. Then we have the label, where we access the label property, and similarly for the type, we access the type property. Great.

    03:20 Let's now jump into our template above here. What we can do as a first step is to render our label, as we now have the necessary information, so we can simply do prop.label. You also need to adjust here the binding to property.key.

    03:35 As you can see, the label rendering property works, so we have it in front of our input field, but the type rendering doesn't yet work. That's because we also have to bind basically on the input type here, and simply specify prop.type.

    03:49 As you can see here, we have a number input field, and we can use the arrow keys to go up and down. Also, entering text won't work.

    Discuss

    Discuss