glazier-react
ReactJS binding using Glazier and Pipes.Fluid
https://github.com/louispan/glazier-react#readme
Version on this page: | 0.4.0.0 |
LTS Haskell 9.21: | 0.6.0.0 |
Stackage Nightly 2018-09-28: | 1.0.0.0 |
Latest on Hackage: | 1.0.0.0 |
glazier-react-0.4.0.0@sha256:e76ef219340c0839dbafbb12d32eb16e2104490a1af8ea6f5ac5946d15b753c6,2397
Module documentation for 0.4.0.0
Glazier.React
contains efficient haskell bindings to React JS where render will only be called for the react components with changed states.
It uses the haskell glazier library to enable composable windows
Features
Efficient rendering
Using React.PureComponent
and react render
will only be called for component who’s state actually changed, instead of requiring react to diff the entire DOM.
Composable widgets
Glazier
allows disciplined and lawful ways of creating composable widgets. Larger can be created out of other widgets without modifying existing widget code, or manual “lifting state” into larger widgets.
For example, List Widget creates a list of any other widget.
Isolation of IO
The stateful effects are pure and do not involve IO. This has the benefit of allowing better testing of the intention of gadgets; increasing confidence of the behaviour of the gadget, reducing the surface area of IO misbehaviour.
There are only two places where IO is allowed:
- in the gadget
Command
interpreter, - in the event callback handlers, due to the need to read properties from
javascript
and dispatchingActions
. Besides dispatchingActions
, it is bad practice to create any other observable side effects in event handlers.
Combine multiple concurrent stateful effects
AFAIK, Haskell is the only language where you can combine multiple concurrent stateful effects consistently.
Compile using GHC as well as GHCJS
Glazier.React
uses ghcjs-base-stub allows compiling GHCJS projects using GHC, which means you can develop using intero.
Easier management of GHCJS callbacks
Glazier.React
uses disposable to ease cleanup of GHCJS callbacks. It also uses a Free Monad Maker
DSL to ease creation of callbacks for widgets.
blaze/lucid style do notation
React elements can be coded using blaze/lucid-style do
notation using ReactMlT
Haskell-driven rendering
All state and processing is in Haskell, meaning only a simple shim React.Component
is required. This reduces the amount of javascript
required and reduces the need for complex stateful integration with React
.
Examples
TodoMVC
This is a fully featured TodoMVC in in Haskell and ReactJS using the glazier-react library.
For a live demo, see https://louispan.github.io/glazier-react-examples/
For more details, see the todo example README.md
Documentation
React
- Please refer to react docs. You only need to read up to handling events.
- Also read Lists and Keys, and Refs and the DOM.
- Ignore controlled input in Forms. In my experience, controlled input is error-prone and it is better to use it uncontrolled.
- Using uncontrolled input doesn’t stop you from subscribing to onChange and obtaining the latest value of the input. Just do not force a render with react
setState
.
- Using uncontrolled input doesn’t stop you from subscribing to onChange and obtaining the latest value of the input. Just do not force a render with react
Glazier
Please read the README.md for a brief overview of glazier.
Markup
Glazier.React.Markup
is a StateT monad that enables blaze/lucid style do
notation to markup React elements to render.
bh (strJS "footer") [("className", strJS "footer")] $ do
bh (strJS "span") [ ("className", strJS "todo-count")
, ("key", strJS "todo-count")] $ do
bh (strJS "strong") [("key", strJS "items")]
(s ^. activeCount . to (txt . pack . show))
txt " items left"
Event handling
React re-uses SyntheticEvent from a pool, which means it may no longer be valid if we lazily parse it. However, we still want lazy parsing so we don’t parse unnecessary fields.
Additionally, we don’t want to block during the event handling.The reason this is a problem is because Javascript is single threaded, but Haskell is lazy. Therefore GHCJS threads are a strange mixture of synchronous and asynchronous threads, where a synchronous thread might be converted to an asynchronous thread if a “black hole” is encountered. See https://github.com/ghcjs/ghcjs-base/blob/master/GHCJS/Concurrent.hs
Glazier.React.Event
uses the event handling idea from the haskell react-flux
library to allow lazy parsing of event safely.
Event handling should only be done via eventHandler
or eventHandlerM
.
eventHandlerM :: (Monad m, NFData a) => (evt -> m a) -> (a -> m b) -> (evt -> m b)
This safe interface requires two input functions:
- a function to reduce SyntheticEvent to a NFData. The mkEventCallback will ensure that the NFData is forced which will ensure all the required fields from Synthetic event has been parsed. This function must not block.
- a second function that uses the NFData. This function is allowed to block.
mkEventHandler results in a function that you can safely pass into ‘GHC.Foreign.Callback.syncCallback1’ with ‘GHCJS.Foreign.Callback.ContinueAsync’.
Simple and efficient React.Component integration
Glazier.React
only uses ReactJS
as a thin layer for rendering and registering event handlers. All state and event processing are performed in Haskell, which means only a simple shim React.PureComponent
is required.
Only one shim React component is ever used and the only methods are required are setState
, render
and componentDidUpdate
,
The shim component only has one thing in it’s state, a sequence number. This sequence number is only changed with setState
when the Glazier.Gadget
determined that there is a need for re-rendering. This is easy and efficient to determine since Gadget
is the StateT
responsible for changing the state in the first place.
This has the benefits of:
- Only the react shim components with changed haskell state will be re-rendered.
- React is able to efficiently determine if state has changed (just a single integer comparison)
- The shim React component is very simple.
Modelling
Glazier.React.Model
contain many nuanced concepts of Model.
Model
The Model
is the pure data used for rendering and stateful logic (the nouns).
It may contain SuperModel
(see below) of other widgets.
Plan
The Plan
contains the callbacks for integrating with React (the verbs). It also contains a javascript reference to the instance of shim component used for the widget. This reference is used to trigger rendering with setState
.
Design
Design
is basically a tuple of Model
and Plan
. It is a separate data type in order to generate convenient lenses to the fields.
Design
is all that a Window
needs to purely generate rendering instructions.
Frame
Frame
is a type synonym of MVar Design
. It is a mutable holder of a copy of Design
. This is so how the official state from Haskell is communicated to the React render
callback. The render
callback will read the latest copy of Design
from the MVar
and pass it to the widget Window
for rendering.
SuperModel
SuperModel
is basically a tuple of Design
and Frame
. It is a separate data type in order to generate convenient lenses to the fields.
This contains everything a widget needs for rendering and state processing.
Most state processing is performed using the pure Design
. The Frame
is only used for the RenderCommand
, to copy the latest Design
into the Frame
when re-rendering is required.
Maker
MVars
for Frame
s and Callback
s for Plan
s may only be created in IO. Using Free Monads, Glazier.React.Maker
provides a safe way to create them without allowing other arbitrary IO.
The Maker
can also be used create the initial SuperModel
state for the widgets.
The Maker
DSL has an action
type parameter which indicated the type of action that is dispatched by the widget.
The action
type can be mapped and hoisted to a larger action
type, allow for embedding the smaller widget action in larger widget actions.
For example, the TodoMVC application uses Maker
to create the initial application SuperModel
which involves making and hoisting the SuperModel
of the input, list of todos widget, and footer widget.
Disposable
GHCJS Callback
s has resources that are not automatically collected by the garbage collector. Callback
s need to be released manually. The disposable library provides a safe and easy way to convert the Callback
into a storable SomeDisposable
that can be queued up to be released after the next rendering frame.
disposable allows generic instances of Disposing
to be easily created, which make it easy to create instances of Disposing
for a Plan
of Callback
s, and therefore the parent containerDesign
, SuperModel
, and Model
(which may contain other widget SuperModel
s)
The List
widget shows how the disposables can be queued for destruction after the next rendered frame.
Widget
A Glazier.React.Widget
is the combination of:
The Maker
instruction on how to create the Plan
of that widget:
mkPlan :: Frame Model Plan -> F (Maker Action) Plan
The rendering instructions for that widget:
window:: WindowT (Design Model Plan) (ReactMlT Identity) ()
The state changes from Action
events:
gadget :: GadgetT Action (SuperModel Model Plan) Identity (DList Command)
This is everything you need in order to create, render and interact with a widget.
Glazier.React.IsWidget
is a typeclass that provides handy XXXOf type functions to get to the type of Command
, Action
, Model
, Plan
of the Widget. It also ensures that the Model
and Plan
is an instance of Disposing
.
instance (CD.Disposing m, CD.Disposing p) =>
IsWidget (Widget c a m p) where
type CommandOf (Widget c a m p) = c
type ActionOf (Widget c a m p) = a
type ModelOf (Widget c a m p) = m
type PlanOf (Widget c a m p) = p
mkPlan (Widget f _ _) = f
window (Widget _ f _) = f
gadget (Widget _ _ f) = f
This is useful for creating widgets that is composed of other Widgets. For example:
The List widget uses the IsWidget typeclass in order to ensure that the itemWidget
can be disposed.
Widget best practices
Please refer to glazier-react-widget
for documentation on the best practices for creating Glazier.React.Widgets