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
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.
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
- in the event callback handlers, due to the need to read properties from
Actions. Besides dispatching
Actions, 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
All state and processing is in Haskell, meaning only a simple shim
React.Component is required. This reduces the amount of
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
- 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
Please read the README.md for a brief overview of glazier.
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 "pieces")]
(s ^. activeCount . to (txt . pack . show))
txt " pieces left"
React re-uses Notice 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.
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.
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
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 Notice 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
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.
Glazier.React.Model contain many nuanced concepts of Model.
Schema is a template of the pure data for stateful logic (the nouns). It is parameterized by a type variable which specializes it to either an
Outline or 'Model'.
Outline is the pure data for stateful logic (the nouns). It may contain 'Outline's of child widgets.
Outline does not contain enough information for rendering the child widgets.
Model is similar to
Outline, except that it may also contain
Gizmos of child widgets.
It may contain
Gizmo (see below) of other widgets.
Model contains enough information to render child widgets, but not this widget.
Scene is basically a tuple of
Plan. It is a separate data type in order to generate convenient lenses to the fields.
Scene is all that a
Window needs to purely generate rendering instructions.
Frame is a type synonym of
MVar Scene. It is a mutable holder of a copy of
Scene. 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
Scene from the
MVar and pass it to the widget
Window for rendering.
Gizmo is basically a tuple of
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
Frame is only used for the
RenderCommand, to put the latest
Scene into the
Frame when re-rendering is required.
Plans may only be created in IO. Using Free Monads,
Glazier.React.Maker provides a safe way to create them without allowing other arbitrary IO.
Maker can also be used create the initial
Gizmo state for the widgets.
Maker DSL has an
action type parameter which indicated the type of action that is dispatched by the widget.
action type can be mapped and hoisted to a larger
action type, allow for embedding the smaller widget action in larger widget actions.
Callbacks has resources that are not automatically collected by the garbage collector.
Callbacks 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
Callbacks, and therefore for the parent container
Model (which may contain other widget
List widget shows how the disposables can be queued for destruction after the next rendered frame.
Glazier.React.Widget is the combination of:
Maker instruction on how to create the
Model of that widget from an
mkModel :: Outline -> F (Maker Action) Model
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 (Scene Model Plan) ReactMl ()
The state changes from
gadget :: Gadget () Action (Gizmo Model Plan) (DList Command)
This is everything you need in order to serialize, deserialize, 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
Plan of the Widget. It also ensures that the
Plan is an instance of
This is useful for creating widgets that is composed of other Widgets.
Please refer to
glazier-react-widget for documentation on the best practices for creating