LSD Metadata
This module provides classes for defining business object metadata in LSD applications.
The metadata is used by other LSD modules, especially LSD Views, to generate common functionality automatically.
The convention used is for the business object class to have a static property entityDescriptor which returns an instance
of EntityDescriptor. This contains an instance of PropertyDescriptor for each stored or computed property.
Further documentation of the classes and their properties and methods is needed, but here is an example
of how the metadata for a business object class called Posting is defined.
In this example the metadata is actually used to help define the class itself: the defaultValues property of EntityDescriptor
is used to define the items stored by the base Record class (from the Immutable.js library)
const {Record} = require('immutable')
, {DebitCredit} = require('./Types')
, Account = () => require('./Account')
, {EntityDescriptor, Reference} = require('lsd-metadata')
const descriptor = new EntityDescriptor("Posting",[
{
name: "account",
type: Reference,
get itemType() { return Account()},
description: "The account for this posting"
},
{
name: "type",
type: DebitCredit,
description: "Debit or Credit"
},
{
name: "amount",
type: Number,
description: "The amount posted to this account"
}
])
class Posting extends Record(descriptor.defaultValues) {
static get entityDescriptor() : Object {
return descriptor
}
constructor(data : Object) {
super(data)
}
setData(name, value) {
return this.set(name, value)
}
toJSON() : Object {
return Object.assign(super.toJSON(), {"@type": this.constructor.name});
}
}
