Property

This class implements the concept of some data holder, that can be configured after construction by some client code. A property is usually used within some kind of component, which needs to hold some specific data portion in order to work, but to delegate the setup of the data to the client code.

A property should be applied for composed data and not so likely for simple types like Boolean, Int or alike. (Prefer to offer a simple public var field for the latter!)

The data should be set by dedicated `operator fun invoke()` methods, that defines the public API for the configuration aspect:

val user = object : Property<User>() {
     // Only visible API for the client, "hide" the complex type by offering the parameters directly!
    operator fun invoke(name: String, alias: String, mail: String) {
         value = User(name, alias, mail)
    }

    // perhaps some other `invoke`s with convenience parameters!
}

A property offers two important functions for the applicator:

• checking whether a value was set ...

• ... and using some other Property's value.

As a client cannot be forced to invoke some Property it is often important to check for the applicator, if some data is present or not in order to fall back to some default behaviour. The Property class offers the isSet property for this use case.

If a component is based upon the headless approach (very likely if you use this part of fritz2's lib), it is common for a component to forward some property to the underlying headless-component. To easily support this feature, the use method exists. Just pass the outer component's Property to the headless component's Property's use method.

Inheritors