tags

#help #example

order

130

description

an init page that uses them

Help: an init page, by example¶✎ edit

A small, complete init page for a portfolio-tracking project, to copy from. A project's own init page is Settings:Init (open it from Admin → Init); this example lives in d2's help, so it isn't compiled or run here.

It does three things: records when the project last started, keeps a running count of holdings as they're added and removed, and notes each release.

---
tags: spec
---
# Init

What this project keeps for itself.

$class Stats (@key id: String, started: String?, holdings: Int?, lastRelease: String?)

When the project starts (and whenever this page is saved):

$when diesel.project.on.init {
  s = dom.find(cls = "Stats", key = "main") ?? {id: "main", holdings: 0}
  dom.upsert(cls = "Stats", entity = s + {started: isoDate(now())})
}

A holding added or removed: keep the count.

$when diesel.entity.on.created (category, key) if (category is "Holding") {
  s = dom.find(cls = "Stats", key = "main") ?? {id: "main", holdings: 0}
  dom.upsert(cls = "Stats", entity = s + {holdings: (s.holdings ?? 0) + 1})
}

$when diesel.entity.on.deleted (category, key) if (category is "Holding") {
  s = dom.find(cls = "Stats", key = "main") ?? {id: "main", holdings: 0}
  dom.upsert(cls = "Stats", entity = s + {holdings: (s.holdings ?? 1) - 1})
}

After a release (Admin → Project):

$when diesel.project.on.released (version) {
  s = dom.find(cls = "Stats", key = "main") ?? {id: "main", holdings: 0}
  dom.upsert(cls = "Stats", entity = s + {lastRelease: version})
}

How it works¶✎ edit

• The spec tag makes the page compiled, like a Spec topic; the lines starting with $ are the rules, the rest is notes for people.
• diesel.project.on.init runs when the project loads and every time you save the page: the place to declare what the project needs, since it runs again whenever you change it.
• diesel.entity.on.created, updated, deleted get the object's category (its class) and key; if (category is "Holding") picks the ones this rule is for. A rule's own writes don't set off more of these, so it can't loop.
• diesel.project.on.released gets the new version.
• Each run is a flow you can open under Flows; a mistake shows there and in the audit log, and never stops the project.

More: LifecycleMessages for every lifecycle message and what it carries, and Expressions for the expressions.