AbstractChainBuilder

The base every chain builder extends. It collects handlers and wires them into a chain.


import { AbstractChainBuilder } from "@drashland/drash/standard/chains/AbstractChainBuilder.js";

It implements IBuilder, leaving build() abstract for the subclass to define.

Members

Member	Kind	Notes
`handlers`	`Handler[]`	Readonly. The handlers collected so far, in the order added.
`handler(handler)`	method	Appends a handler. Returns `this`, so calls chain.
`build()`	abstract	The subclass decides what to assemble and what to return.
`link()`	protected	Wires `handlers` together and returns the head.

`link()`

Reduces the collected handlers with setNext(), so each points at the next, then returns handlers[0] — the head, and the object whose handle() you call.

It validates first, and throws a plain Error (not an HTTPError) if the list is unusable:


Chain.Builder: `this.handlers` should be an array
Chain.Builder: `this.handlers` is empty

Both messages are prefixed Chain.Builder:, which names a class that no longer exists — useful to know if you are grepping for the source of one.

The One Subclass

RequestChainBuilder (modules/builders/RequestChainBuilder.js) is the only subclass that ships. Its build() assembles the request chain’s five handlers in a fixed order and returns the head.

handler() and handlers are deliberately absent from what Application.builder() hands you. The request chain’s handlers, and the order they run in, are decided by build() and are not the consumer’s to change — so the public type exposes three methods and nothing else. See Handlers for the handlers themselves and the order they run in.

Extending AbstractChainBuilder yourself is the supported way to assemble a chain that is not the request chain.