chain-of-responsibility
v0.3.0
Published
Extendable classes for Chain of Responsibility pattern.
Downloads
14
Maintainers
Readme
chain-of-responsibility
About pattern
Description of "Chain of Responsibility" pattern
Installation
npm install chain-of-responsibility
Usage
Import classes:
import * as ChainOfResponsibility from '../dist/chain-of-responsibility.js'
const {AbstractChainItem, AbstractChainItemValueContainer, AbstractChainItemContainer} = ChainOfResponsibility;
Create chain items:
class ChainParkingLotBegin extends AbstractChainItem {
_execute(valueContainer) {
valueContainer.addToCharge(valueContainer.getParameter('entry'));
}
}
class ChainParkingLotFirstHour extends AbstractChainItem {
_execute(valueContainer, resolve) {
valueContainer.subtractSeconds(3600);
valueContainer.addToCharge(valueContainer.getParameter('first_hour'));
setTimeout(() => {
resolve();
}, 2000);
}
shouldStopAfter(valueContainer) {
return valueContainer.getValue('seconds') <= 0;
}
}
If Chain Item was created with async flag in _execute
method there is second parameter available which is
resolve function.
class ChainParkingLotRestHours extends AbstractChainItem {
_execute(valueContainer) {
let seconds = valueContainer.getValue('seconds');
valueContainer.subtractSeconds(seconds);
valueContainer.addToCharge(Math.ceil(seconds / 60 / 60) * valueContainer.getParameter('after_first_hour'));
}
shouldStopAfter(valueContainer) {
return valueContainer.getValue('seconds') <= 0;
}
}
Chain Item flow methods
In AbstractChainItem
class you can modify the Chain Stack flow.
The following methods are available:
shouldStopBefore
shouldStopAfter
shouldSkip
and should return booleans.
Create chain items container:
class ParkingLotChainItemContainer extends AbstractChainItemContainer {
_createItemsChain(first) {
let stack1 = first;
let stack2 = new ChainParkingLotFirstHour(this, true);
let stack3 = new ChainParkingLotRestHours(this);
stack1.setNextChainItem(stack2);
stack2.setNextChainItem(stack3);
}
_getFirstChainItem() {
return new ChainParkingLotBegin(this);
}
}
Second parameter in new ChainParkingLotFirstHour(this, true);
describes if Chain Item is async.
Create value container:
class ParkingLotValueContainer extends AbstractChainItemValueContainer {
_parseValue(seconds) {
return {
charge: 0,
seconds
};
}
getResult() {
return this.getValue('charge');
}
addToCharge(charge) {
let value = this.getValue('charge');
value += charge;
this.setValue('charge', value);
return this;
}
subtractSeconds(seconds) {
let value = this.getValue('seconds');
value -= seconds;
this.setValue('seconds', value);
return this;
}
}
Use created classes:
let charger = new ParkingLotChainItemContainer(new ParkingLotValueContainer(12060, {
'entry': 2,
'first_hour': 3,
'after_first_hour': 4
}));
let promise = charger.run();
promise.then((result) => {
console.log("promised", result); // promised 17
});
let result = charger.getResult();
console.log(result); // 5