Development note · Custom Component
Custom components support only 'simpler data' types — scalars, strings, SIMD values, and enums — with Xcode build-time errors for unsupported types.
Apple's WWDC 2023 session 'Work with Reality Composer Pro content in Xcode' explicitly defines custom component type constraints. The session demonstrates PointOfInterestComponent with String, custom enum, and Optional<String> fields, and warns that Xcode produces errors for types RCP cannot serialize.
Metadata
Reproduction
- Watch WWDC 2023 session 'Work with Reality Composer Pro content in Xcode' (wwdc2023-10273).
- Navigate to ~22:31 where the speaker discusses custom component type constraints.
- Observe the PointOfInterestComponent example showing String, enum, and Optional<String> fields.
- Note the explicit warning: 'You'll see an error in your Xcode project if you add a property to your custom component that's of a type that Reality Composer Pro won't serialize.'
- Cross-reference demonstrated types with the USD-serializable subset (bool, int, uint, float, double, string, token, float2/3/4, quatf).
Evidence
-
Official Apple session documenting custom component type constraints at ~22:31
-
52 Swift types tested against RCP — confirms the 'simpler data' constraint
Details
Source
WWDC 2023 session “Work with Reality Composer Pro content in Xcode” (wwdc2023-10273).
At 22:31:
“Design-time components are for housing simpler data, such as ints, strings, and SIMD values, things that 3D artists and designers will make use of.”
And:
“You’ll see an error in your Xcode project if you add a property to your custom component that’s of a type that Reality Composer Pro won’t serialize.”
Example from the Session
The session demonstrates a PointOfInterestComponent example:
public struct PointOfInterestComponent: Component, Codable {
public var region: Region = .yosemite // Custom enum (serializes as string/token)
public var name: String = "Ribbon Beach"
public var description: String? // Optional String
}Supported Type Categories
| Category | Swift Types | USD Type | Status |
|---|---|---|---|
| Scalars | Bool, Int, UInt, Float, Double, String | bool, int, uint, float, double, string | ✓ Supported |
| Optionals | String?, scalar optionals | Same as base type | ✓ Supported |
| SIMD | SIMD2<Float>, SIMD3<Float>, SIMD4<Float>, simd_quatf | float2, float3, float4, quatf | ✓ Supported |
| Enums | Custom string-based enums | token | ✓ Supported |
| Arrays | [Bool], [Int], [Float], etc. | bool[], int[], float[] | ✗ Not supported |
What to Avoid
The session’s “simpler data” constraint explicitly excludes:
| Unsupported Type | Example | Why It Fails |
|---|---|---|
| Entity references | Entity? | Use rel relationships instead |
| Complex nested structs | Nested Codable | Only simple enums serialize |
| Runtime-only types | ObjectIdentifier | Not USD-serializable |
| Half-precision SIMD | SIMD3<Float16> | No half3 support in RCP |
| Integer vectors | SIMD3<Int32> | No int3 support in RCP |
Build-Time Validation
Unlike runtime errors, RCP provides compile-time feedback through Xcode:
RCP generates Swift code from the USD schema
↓
Xcode attempts to compile the generated code
↓
Build fails with clear error for unsupported typesThis makes custom components self-documenting — the supported types are exactly those that survive the codegen → compile pipeline.
Inspector-Safe Type Palette
For custom component field editing in Deconstructed, use these verified types:
| # | Category | Swift Types |
|---|---|---|
| 1 | Scalars | Bool, Int, UInt, Float, Double, String |
| 2 | Optionals | Bool?, Int?, Float?, String? |
| 3 | SIMD | SIMD2<Float>, SIMD3<Float>, SIMD4<Float>, simd_quatf |
| 4 | Enums | String or Int raw-value enums |
| 5 | Arrays | ⚠️ Currently unsupported in RCP |