Stores.md

Stores

Stores are observable objects that contain a value.

Each store has a subscribe() method which allows the execution of a callable whenever the value of the store changes, this callable provides the new value of the store as a parameter.

Stores can be of 2 types

• Writable stores
• Readable stores

Writable

You can read and write values in a writable store.

You can set the value on creation or some time after by using the set() method.

use function CatPaw\Store\Writable;

function main() {
    $store = new Writable("A");       // set on creation
    echo $store->get().PHP_EOL;           // will print "A"
    $store->set("B");                     // changing the value
    echo $store->get().PHP_EOL;           // will print "B"
}

Use subscribe() to watch over the value of the store.

Note

Remember to $unsubscribe() from the store after you're done with it.

use function CatPaw\Store\Writable;

function main() {
    $store       = new Writable("A");
    $unsubscribe = $store->subscribe(static function($value) {
        echo $value.PHP_EOL;
    });
    $store->set("B");

    $unsubscribe();
    // Unsubscribing here means the
    // following `$store->set("C")` call
    // will not trigger any subscribers.

    $store->set("C");
}

Output

A
B

Notice how it doesn't print C; that is because by the time C is set, $unsubscribe() has already been invoked.

Readable

You can only read values from a readable store.

use function CatPaw\Store\Readable;

function main() {
    $store = new Readable("default value", static function($set) {
        $set("hello world");
    });

    
    $unsubscribe = $store->subscribe(static function($value){
        echo $value.PHP_EOL;
    })

    $unsubscribe();
}

Output

default value
hello world