Field components
Both the naming and the way the components work are based on being data-driven.
Standardized properties
All input component has a fixed set of props that make it possible to build more complex standardized functionality around them. The most important ones here are value and onChange. Value expects values in the given data type, so for example Field.Number expects a value of the type number, and will give a type error in Typescript if it e.g. receives a number in a string. The callback function submitted to onChange will always receive the value of the corresponding type as the first argument.
It is deliberate that onChange sends out the value from the field, and not the event object that comes from the actual HTML tag into which the user enters data. This is to create a less tight coupling between application code that uses the components, and the internal implementation in the field components. In addition, this makes the surrounding logic simpler by not having to extract, for example, e.target.value everywhere.
The basic components have a number of properties that make it possible to control how they function in the interface, such as multiline on Field.String, which chooses whether to get one line of text (input tag) or several lines (textarea tag) . In addition, they have a number of validation props, such as minLength and required.
Controlled & Uncontrolled
In React, it's important to be aware of where the states of a given set of data "lives". This can be an entire object that represents an entity the user is going to make changes to (e.g. a user or a bank account), but it also applies to the individual value a form makes changes to. A form field can be controlled or uncontrolled. The components in this package make it possible to work in both ways.
If the functionality is designed so that the state of the data will live outside the form components, you give the components a value and an onChange, and ensure that all changes that are sent out via onChange are fed back via value so that it functions as a controlled component. The internal logic in the components will then ensure that the value is kept the same via the changes it receives from the outside.
If you want the state of the value to live inside the input component, do not send the updated value in via value. The logic will then keep the internal value with the changes continuously, and still send the latest version with all the changes the user has made, even if they are not received continuously via value, as a basic <input> tag in React expects.
Creating custom field components
The useField hook that is used in all existing field components is exported to make it possible to create custom field components that have the same properties and follow the same flow as the standard components, without the need to recreate all the basic state handling features.