purescript-observable

Observables for PureScript, compatible with the ECMAScript Observable proposal.

API docs on Pursuit

Usage

A basic usage example:

module Main where

import Prelude
import Control.Monad.Eff.Console (log)
import Control.Monad.Eff.Exception (message)
import Control.Observable (fromFoldable, subscribe)
import Data.String (toUpper)

main = do
  let o = toUpper <$> fromFoldable ["hello", "world"]
  subscribe {
    next: log,
    error: message >>> log,
    complete: pure unit
    } o

Creating custom streams:

module Main where

import Prelude
import Control.Monad.Eff.Console (log)
import Control.Monad.Eff.Exception (message)
import Control.Observable (observable, subscribe, free)

main = do
  o <- observable \sink -> do
    sink.next "Hello Joe"
    sink.next "Hello Mike"
    sink.next "Hello Robert"
    sink.complete
    free []

  -- `observe` is a shorthand for `subscribe`
  observe log (message >>> log) (pure unit) o

ECMAScript Observable Compatibility

The observables created by this library should be fully compatible with the ECMAScript Observable proposal. You should also be able to consume any observable implementing the specification using this library, if you cast it to the Observable type.

FAQ

Q: Why isn't every operation effectful?

A: Only operations which may need to utilise effects themselves are effectful. This includes creating new observables, subscribing to an observable, and not much else. Creating a new observable by eg. mapping a pure function over an existing observable is itself a pure function - it's true that if you perform such an operation twice you'll have two different observables, but they'll always emit the exact same events at the exact same time, meaning that they have value equality.

Licence

This program is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this program. If not, see http://www.gnu.org/licenses/.

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