ViewModels

Location: backend/state/viewmodelregistry.h / backend/state/viewmodelregistry.cpp

ViewModels is the singleton registry and ownership gate for MVVM model objects.

Purpose

• Register model objects by key.
• Bind view ids to keys.
• Enforce single-writer ownership semantics.

Properties

• keys: stringList
• views: stringList
• bindings: map
• owners: map
• lastError: string

Registration APIs

• set(key, object)
• get(key)
• remove(key)
• clear()

Binding and Ownership APIs

• bindView(viewId, key, writable = false)
• unbindView(viewId)
• getForView(viewId)
• keyForView(viewId)
• claimOwnership(viewId, key)
• releaseOwnership(viewId, key?)
• canWrite(viewId, key?)
• ownerOf(key)

Property Access APIs

• updateProperty(viewId, property, value)
• updatePropertyByKey(viewId, key, property, value)
• readProperty(viewId, property)

Write Guard Semantics

Write updates fail when:

• view id is empty,
• view has no binding,
• view is not owner of target key,
• key/object/property is invalid.

On failure, API returns false and updates lastError.

Usage Example

import LVRS 1.0 as LV

Component.onCompleted: {
    LV.ViewModels.set("Dashboard", dashboardVm)
    LV.ViewModels.bindView("DashboardPage", "Dashboard", true)
}

function setStatus(nextStatus) {
    if (!LV.ViewModels.updateProperty("DashboardPage", "status", nextStatus))
        console.warn(LV.ViewModels.lastError)
}

Internal Behavior Notes

• Tokens are trim-normalized.
• Stale bindings/owners are pruned when keys vanish.
• Objects parented by registry may be auto-disposed when no key references remain.

Extended Example: Explicit Ownership Transfer

import LVRS 1.0 as LV

function transferOwner(fromView, toView, key) {
    LV.ViewModels.releaseOwnership(fromView, key)
    if (!LV.ViewModels.claimOwnership(toView, key))
        console.warn(LV.ViewModels.lastError)
}

Review Checklist

• every writable view must have explicit ownership claim,
• read-only views should bind with writable=false,
• lastError must be surfaced in developer tooling for failed writes.

FAQ

Q. Can two views write to one key simultaneously?
A. No. Ownership model is single-writer by contract.