Authoring screens

Murti renders screens from JSON. MurtiBuilder is a Swift DSL that produces that JSON, so you can write screens in typed Swift instead of by hand, and MurtiGen turns authored screens into validated JSON files at build time.

Both run on Apple platforms and depend on MurtiCore.

The DSL

import MurtiBuilder

let dashboard = Screen("dashboard") {
    VStack(spacing: 12, alignment: .leading) {
        Text("Hello, {{user.name}}", style: .title)
        Button("View details",
               action: .navigate("productDetail", params: ["productId": "abc123"]))
        Button("Load balance",
               action: .api("getAccountBalance", onSuccess: .navigate("balanceDetail")))
    }
}

let json = try dashboard.validated().jsonData()

{{user.name}} stays in the output verbatim; the app resolves tokens at render time. validated() runs the schema validator and throws if the screen is invalid; jsonData() encodes the payload (with sorted keys, so output is stable).

Built-in components

Text, Image, VStack, HStack, Button, and Card cover the built-in component set. Containers take a child closure; the closure supports if and for:

VStack(spacing: 8) {
    if showHeader { Text("Recent", style: .headline) }
    for item in items { Text(item.title) }
}

Any other component

The built-ins mirror the renderer's built-in set, but the registry is open. Use component(_:_:) to author a third-party or custom type by its type string:

component("lottie", ["name": "success_check", "loop": false])
component("rating", ["stars": 4])

Actions

Button takes an Action: .navigate(_:params:onSuccess:onError:), .api(_:params:onSuccess:onError:), .dismiss, .refresh, or .openURL(_:). Targets are named references (a screen key, a named request, a named link), never a raw URL.

A note on names

Text, VStack, Button, and Image share names with SwiftUI. Write screen-authoring files that import MurtiBuilder but not SwiftUI; if a file needs both, qualify the DSL type as MurtiBuilder.Text.

Export as DSL

DSLExport runs the DSL in reverse: given a decoded tree (a MurtiNode or a full MurtiPayload), it generates MurtiBuilder source that rebuilds an equivalent tree. The visual editor uses it for its Export DSL button, so a screen imported as JSON — or built by direct manipulation — can come back out as Swift.

import MurtiBuilder

let source = DSLExport.source(for: payload)   // a String of MurtiBuilder code

A node is written with its typed initializer (Text, VStack, Button, …) when its props fit that initializer exactly; anything else falls back to the open-vocabulary component("type", [props]) { … } so no props are lost. Node ids aren't emitted (the DSL doesn't set them), matching JSON export. An action on a non-button has no DSL form, so it's omitted with a note in the output.

Build-time generation

MurtiGen writes each authored screen to <key>.json, validating every screen first so a bad bundle never ships. Author screens in Sources/MurtiGen/main.swift (loop over data for lists), then run:

swift run MurtiGen Generated

Serve the resulting JSON from any backend or CDN as opaque bytes. The structure is fixed at generation time; dynamic values stay at runtime through {{token}}s and named API requests. To ship signed, production-ready payloads, wrap the output in a signed envelope (see the security model) as part of your build.