fritz2 is an extremely lightweight, well-performing, independent library for building reactive web apps in Kotlin, heavily depending on coroutines and flows.
fritz2 includes an intuitive way to build and render HTML elements using a type-safe dsl. You can easily create lightweight reactive HTML components which are bound to an underlying model and automatically change whenever the model data changes:
val model = storeOf("init value")
render {
div("some-css-class") {
input {
value(model.data)
changes.values() handledBy model.update
}
p {
+"model value = "
model.data.renderText()
}
}
}fritz2 implements precise data binding. This means that when parts of your data model change, exactly those and only those DOM-nodes depending on the changed parts will automatically change as well. No intermediate layer (like a virtual DOM) is needed. fritz2 requires no additional methods to decide which parts of your component have to be re-rendered. fritz2 also supports two-way data binding out-of-the-box to update your model by listening on events:
Utilizing Kotlin's multiplatform-abilities, you'll write the code of your data classes only once and use it on your client and server (i.e. in a SpringBoot- or Ktor-Backend). This is also true for your model-validation-code, which can quickly become far more complex than your data model.
Key Features
- easy reactive one- and two-way data binding (even for lists and deep nested structures)
- hassle-free state-handling
- model-validation and message handling
- http and websockets
- hash-based routing
- history / undo
- processing state ("spinning wheel")
- webcomponents
- easy to learn
- documentation
- examples i.e. implementing the specification of TodoMVC
How to try it?
- Take a look at our hosted examples
- Or set up a new project on your own, following our documentation
Overall Goals
- staying lightweight
- keeping dependencies as low as possible
- providing tags, attributes, events for HTML from specification (w3c, mozilla, ...)
- making it as easy as possible to write reactive web-apps in pure kotlin
Inspiration
fritz2 is hugely inspired by the great Binding.scala framework. Later we discovered that a lot of those concepts are described independently in Meiosis. Also, fritz2 relies heavily on the great Kotlin coroutines library.
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