reactives 0.2.0

A declarative reactive programming framework.

Reactives

Reactives lets you write reactive code easily by making any of your objects and functions reactive. A reactive can be triggered (reactive.react.trigger()), causing all its reactors to be called. A reactor is any callable that takes no arguments, and you add it to a reactive via reactive.react(reactor). When a reactive is triggered, its reactors and its reactors' reactors are resolved, and each is called once in order.

Reactives uses a push-pull approach, meaning change notifications are pushed (reactors are called automatically and won't have to pull for changes), but if a reactor needs to know what exactly changed, it must pull this information itself.

Usage

For any type to be reactive, it must have a react attribute containing a reactives.ReactorController. The most common way to achieve this, is to decorate that type with @reactives.reactive. Some classes are provided that are reactive and can be instantiated or inherited from directly.

Custom classes

Decorate a class to make its individual instances reactive:

from reactives import reactive

@reactive
class Apple:
    pass

apple = Apple()
apple.react(lambda: print('The apple got triggered!'))
apple.react.trigger()
# >>> "The apple got triggered!"

Functions and methods

Decorate a function:

from reactives import reactive

@reactive
def apple():
    pass

apple.react(lambda: print('The apple got triggered!'))
apple.react.trigger()
# >>> "The apple got triggered!"

Decorate a method on a reactive class:

from reactives import reactive

@reactive
class Apple:
    @reactive
    def apple(self):
        pass

apple = Apple()
apple.react.getattr('apple').react(lambda: print('The apple got triggered!'))
apple.react.getattr('apple').react.trigger()
# >>> "The apple got triggered!"

Reactive methods must be accessed through their instance, because Apple.apple would yield the class method.

Both functions and methods can be called automatically when they're triggered. This lets them set up something once, and update that thing when they're triggered:

from reactives import reactive

@reactive(on_trigger_call=True)
def warm_caches():
    """
    Warm the application's caches. When triggered (because the cached data has changed), re-warm the caches.
    """
    pass

Properties

Decorate a property:

from reactives import reactive

@reactive
class Apple:
    @reactive
    @property
    def apple(self) -> str:
        return 'I got you something!'

apple = Apple()
apple.react.getattr('apple').react(lambda: print('The apple got triggered!'))
apple.react.getattr('apple').react.trigger()
# >>> "The apple got triggered!"

If a property deleter is present, it will be called automatically when the property is triggered:

from reactives import reactive

@reactive
class Apple:
    def __init__(self):
        self._computed_something = None

    @reactive
    @property
    def apple(self) -> str:
        if self._computed_something is None:
            self._computed_something = 'I got you something!'
        return self._computed_something

    @apple.deleter
    def apple(self)  -> None:
        self._computed_something = 'I got you nothing!'

apple = Apple()
print(apple.apple)
# >>> "I got you something!"
apple.react.getattr('apple').react().trigger()
print(apple.apple)
# >>> "I got you nothing!"

If you do not want automatic deletion, configure the property's @reactive decorator as such:

from reactives import reactive

@reactive
class Apple:
    def __init__(self):
        self._computed_something = None

    @reactive(on_trigger_delete=False)
    @property
    def apple(self) -> str:
        if self._computed_something is None:
            self._computed_something = 'I got you something!'
        return self._computed_something

    @apple.deleter
    def apple(self)  -> None:
        self._computed_something = 'I got you nothing!'

apple = Apple()
print(apple.apple)
# >>> "I got you something!"
apple.react.getattr('apple').react().trigger()
print(apple.apple)
# >>> "I got you something!"

Property setters work exactly like with any other property:

from reactives import reactive

@reactive
class Apple:
    def __init__(self):
        self._something = 'I got you something!'

    @reactive
    @property
    def apple(self) -> str:
        return self._something

    @apple.setter
    def apple(self, something: str):
        self._something = something

apple = Apple()
apple.react.getattr('apple').react(lambda: print('The apple got triggered!'))
apple.apple = 'I got you something else!'
# >>> "The apple got triggered!"

Values set through a property may themselves be reactive too. If they are, the property and the value are autowired, which means that the property becomes a reactor to the newly added value. As soon as the value is triggered, so is the property. Therefore, if you want to react to any change to any of the values a property might have, all you need to do is add your reactor to the property.

Lists

ReactiveList is a reactive version of Python's built-in list. You can use it in exactly the same way as list:

from reactives import ReactiveList

fruits = ReactiveList(['apple', 'banana'])
fruits.react(lambda: print('Look at all these delicious fruits!'))
fruits.append('orange')
# >>> "Look at all these delicious fruits!"

Values added to a ReactiveList may themselves be reactive too. If they are, the list and the value are autowired, which means that the list becomes a reactor to the newly added value. As soon as the value is triggered, so is the list. Therefore, if you want to react to any change to any of the values in a ReactiveList, all you need to do is add your reactor to the list.

Dictionaries

ReactiveDict is a reactive version of Python's built-in dict. You can use it in exactly the same way as dict:

from reactives import ReactiveDict

fruits = ReactiveDict(apple=5, banana=2)
fruits.react(lambda: print('Look at all these delicious fruits!'))
fruits['orange'] = 4
# >>> "Look at all these delicious fruits!"

Values added to a ReactiveDict may themselves be reactive too. If they are, the dictionary and the value are autowired, which means that the dictionary becomes a reactor to the newly added value. As soon as the value is triggered, so is the dictionary. Therefore, if you want to react to any change to any of the values in a ReactiveDict, all you need to do is add your reactor to the dictionary.

Autowiring

We've seen how properties, lists, and dictionaries autowire themselves to their values. This is possible because properties, lists, and dictionaries know exactly which values move in and out of them. In other cases, we use scope. Any reactive can start a scope with reactives.scope.collect() and collect all reactives that are called or used during that scope window, and autowire itself to them. Conversely, any reactive can register itself with the current scope (if there is one) with reactives.scope.register*(), and allow reactives depending on it to autowire themselves. In fact, this is what properties do internally.

Autowiring means that as a developer, you won't need to worry about connecting the parts of your application most of the time.

Development

First, fork and clone the repository, and navigate to its root directory.

Requirements

• Bash (you're all good if which bash outputs a path in your terminal)

Installation

If you have tox installed on your machine, tox --develop will create the necessary virtual environments and install all development dependencies.

Alternatively, in any existing Python environment, run ./bin/build-dev.

Testing

In any existing Python environment, run ./bin/test.

Fixing problems automatically

In any existing Python environment, run ./bin/fix.

Contributions 🥳

Reactives is Free and Open Source Software. As such you are welcome to report bugs or submit improvements.

Copyright & license

Reactives is copyright Bart Feenstra and contributors, and released under the GNU General Public License, Version 3. In short, that means you are free to use Reactives, but if you distribute Reactives yourself, you must do so under the exact same license, provide that license, and make your source code available.