# Reactive Form

Reactive forms offer the ease of using reactive patterns, testing, and validation.

You create and manipulate form control objects directly in the **component** class.

As the component class has immediate access to both the **data model** and the **form control structure**, you can push data model values into the form controls and pull user-changed values back out.

The component can observe changes in form control state and react to those changes.

## Immutability of the data model

In keeping with the reactive paradigm, the component preserves the **immutability** of the **data model**, treating it as a pure source of original values.

Rather than update the data model directly, the component extracts user changes and forwards them to an **external component** or **service**, which does something with them (such as saving them) and returns a **new** **data model** to the component that reflects the updated model state.

A **FormControl** constructor accepts three, optional arguments:

* the initial data value
* an array of validators
* an array of async validators

Fundamental Class