Summary
BridgeJS needs a typed closure handle type that preserves object identity across the Swift/JS bridge. We're looking for community input on naming.
Background
JavaScriptKit already has JSClosure for untyped closures:
let closure = JSClosure { args -> JSValue in
// ...
}For BridgeJS, we need a typed variant with a generic parameter for the function signature. This enables type-safe declarations like:
@JSFunction func addEventListener(_ type: String, _ listener: (MessageEvent) -> Void)
The typed closure handle is essential for APIs like addEventListener/removeEventListener that require stable object identity, passing the same closure reference to both calls.
Related issues
Constraints
- Must coexist with
JSClosure: we can't simply make JSClosure<T> generic (breaking change)
- Explicit conversion required: Swift doesn't support implicit conversion from closure literals, so users will write the type name frequently
Candidates
1. Nested type: JSClosure.Typed<T>
@JSClass struct JSHTMLElement {
@JSFunction func addEventListener(_ type: String, _ listener: JSClosure.Typed<(MessageEvent) -> Void>)
@JSFunction func removeEventListener(_ type: String, _ listener: JSClosure.Typed<(MessageEvent) -> Void>)
}
let handler = JSClosure.Typed<(MessageEvent) -> Void> { event in
print(event.data)
}
document.addEventListener("load", handler)
document.removeEventListener("load", handler)
@JSFunction func requestAnimationFrame(_ callback: JSOneshotClosure.Typed<(Double) -> Void>)
requestAnimationFrame(JSOneshotClosure.Typed { timestamp in
print(timestamp)
})
- Clear relationship to
JSClosure
- Discoverable via autocomplete
- Verbose (15 characters)
2. JSTypedClosure<T>
@JSClass struct JSHTMLElement {
@JSFunction func addEventListener(_ type: String, _ listener: JSTypedClosure<(MessageEvent) -> Void>)
@JSFunction func removeEventListener(_ type: String, _ listener: JSTypedClosure<(MessageEvent) -> Void>)
}
let handler = JSTypedClosure<(MessageEvent) -> Void> { event in
print(event.data)
}
document.addEventListener("load", handler)
document.removeEventListener("load", handler)
@JSFunction func requestAnimationFrame(_ callback: JSTypedClosure<(Double) -> Void>)
requestAnimationFrame(JSTypedClosure.oneshot { timestamp in
print(timestamp)
})3. JSCallback<T>
@JSClass struct JSHTMLElement {
@JSFunction func addEventListener(_ type: String, _ listener: JSCallback<(MessageEvent) -> Void>)
@JSFunction func removeEventListener(_ type: String, _ listener: JSCallback<(MessageEvent) -> Void>)
}
let handler = JSCallback<(MessageEvent) -> Void> { event in
print(event.data)
}
document.addEventListener("load", handler)
document.removeEventListener("load", handler)
@JSFunction func requestAnimationFrame(_ callback: JSCallback.Oneshot<(Double) -> Void>)
requestAnimationFrame(JSCallback.Oneshot { timestamp in
print(timestamp)
})3. [Need your input]
Summary
BridgeJS needs a typed closure handle type that preserves object identity across the Swift/JS bridge. We're looking for community input on naming.
Background
JavaScriptKit already has
JSClosurefor untyped closures:For BridgeJS, we need a typed variant with a generic parameter for the function signature. This enables type-safe declarations like:
The typed closure handle is essential for APIs like
addEventListener/removeEventListenerthat require stable object identity, passing the same closure reference to both calls.Related issues
Constraints
JSClosure: we can't simply makeJSClosure<T>generic (breaking change)Candidates
1. Nested type:
JSClosure.Typed<T>JSClosure2.
JSTypedClosure<T>3.
JSCallback<T>3. [Need your input]