Add JSBridgedType and JSBridgedClass

Sources/JavaScriptKit/BasicObjects/JSArray.swift

@@ -1,48 +1,56 @@
-public class JSArray {
-    static let classObject = JSObject.global.Array.function!
+public class JSArray: JSBridgedClass {
+    public static let constructor = JSObject.global.Array.function!
 
     static func isArray(_ object: JSObject) -> Bool {
-        classObject.isArray!(object).boolean!
+        constructor.isArray!(object).boolean!
     }
 
-    let ref: JSObject
+    public let jsObject: JSObject
 
-    public init?(_ ref: JSObject) {
-        guard Self.isArray(ref) else { return nil }
-        self.ref = ref
+    public required convenience init?(from value: JSValue) {
+        guard let object = value.object else { return nil }
+        self.init(object)
+    }
+
+    public convenience init?(_ jsObject: JSObject) {
+        guard Self.isArray(jsObject) else { return nil }
+        self.init(withCompatibleObject: jsObject)
+    }
+    public required init(withCompatibleObject jsObject: JSObject) {
+        self.jsObject = jsObject
     }
 }
 
 extension JSArray: RandomAccessCollection {
     public typealias Element = JSValue
 
     public func makeIterator() -> Iterator {
-        Iterator(ref: ref)
+        Iterator(jsObject: jsObject)
     }
 
     public class Iterator: IteratorProtocol {
-        let ref: JSObject
+        let jsObject: JSObject
         var index = 0
-        init(ref: JSObject) {
-            self.ref = ref
+        init(jsObject: JSObject) {
+            self.jsObject = jsObject
         }
 
         public func next() -> Element? {
             let currentIndex = index
-            guard currentIndex < Int(ref.length.number!) else {
+            guard currentIndex < Int(jsObject.length.number!) else {
                 return nil
             }
             index += 1
-            guard ref.hasOwnProperty!(currentIndex).boolean! else {
+            guard jsObject.hasOwnProperty!(currentIndex).boolean! else {
                 return next()
             }
-            let value = ref[currentIndex]
+            let value = jsObject[currentIndex]
             return value
         }
     }
 
     public subscript(position: Int) -> JSValue {
-        ref[position]
+        jsObject[position]
     }
 
     public var startIndex: Int { 0 }
@@ -62,14 +70,14 @@ extension JSArray: RandomAccessCollection {
     /// array.count  // 2
     /// ```
     public var length: Int {
-        return Int(ref.length.number!)
+        Int(jsObject.length.number!)
     }
 
     /// The number of elements in that array **not** including empty hole.
     /// Note that `count` syncs with the number that `Iterator` can iterate.
     /// See also: `JSArray.length`
     public var count: Int {
-        return getObjectValuesLength(ref)
+        getObjectValuesLength(jsObject)
     }
 }
 

Sources/JavaScriptKit/BasicObjects/JSDate.swift

@@ -6,9 +6,9 @@ in the naming. Parts of the JavaScript `Date` API that are not consistent across
 implementations are not exposed in a type-safe manner, you should access the underlying `jsObject`
 property if you need those.
 */
-public final class JSDate {
+public final class JSDate: JSBridgedClass {
     /// The constructor function used to create new `Date` objects.
-    private static let constructor = JSObject.global.Date.function!
+    public static let constructor = JSObject.global.Date.function!
 
     /// The underlying JavaScript `Date` object.
     public let jsObject: JSObject
@@ -39,6 +39,10 @@ public final class JSDate {
         jsObject = Self.constructor.new(year, monthIndex, day, hours, minutes, seconds, milliseconds)
     }
 
+    public init(withCompatibleObject jsObject: JSObject) {
+        self.jsObject = jsObject
+    }
+
     /// Year of this date in local time zone.
     public var fullYear: Int {
         get {

Sources/JavaScriptKit/BasicObjects/JSError.swift

@@ -2,9 +2,9 @@
 class](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error) that
 exposes its properties in a type-safe way.
 */
-public final class JSError: Error {
+public final class JSError: Error, JSBridgedClass {
     /// The constructor function used to create new `Error` objects.
-    private static let constructor = JSObject.global.Error.function!
+    public static let constructor = JSObject.global.Error.function!
 
     /// The underlying JavaScript `Error` object.
     public let jsObject: JSObject
@@ -14,6 +14,10 @@ public final class JSError: Error {
         jsObject = Self.constructor.new([message])
     }
 
+    public init(withCompatibleObject jsObject: JSObject) {
+        self.jsObject = jsObject
+    }
+
     /// The error message of the underlying `Error` object.
     public var message: String {
         jsObject.message.string!

Sources/JavaScriptKit/BasicObjects/JSTypedArray.swift

@@ -4,51 +4,48 @@
 
 import _CJavaScriptKit
 
+/// A protocol that allows a Swift numeric type to be mapped to the JavaScript TypedArray that holds integers of its type
 public protocol TypedArrayElement: JSValueConvertible, JSValueConstructible {
+    /// The kind of typed array that should be created on the JS side
     static var typedArrayKind: JavaScriptTypedArrayKind { get }
+    /// The constructor function for the TypedArray class for this particular kind of number
     static var typedArrayClass: JSFunction { get }
 }
 
-public class JSTypedArray<Element>: JSValueConvertible, ExpressibleByArrayLiteral where Element: TypedArrayElement {
-    let ref: JSObject
-    public func jsValue() -> JSValue {
-        .object(ref)
-    }
+/// A wrapper around all JavaScript [`TypedArray`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray) classes that exposes their properties in a type-safe way.
+public class JSTypedArray<Element>: JSBridgedClass, ExpressibleByArrayLiteral where Element: TypedArrayElement {
+    public static var constructor: JSFunction { Element.typedArrayClass }
+    public var jsObject: JSObject
 
     public subscript(_ index: Int) -> Element {
         get {
-            return Element.construct(from: getJSValue(this: ref, index: Int32(index)))!
+            return Element.construct(from: jsObject[index])!
         }
         set {
-            setJSValue(this: ref, index: Int32(index), value: newValue.jsValue())
+            self.jsObject[index] = newValue.jsValue()
         }
     }
 
-    // This private initializer assumes that the passed object is TypedArray
-    private init(unsafe object: JSObject) {
-        self.ref = object
-    }
-
-    public init?(_ object: JSObject) {
-        guard object.isInstanceOf(Element.typedArrayClass) else { return nil }
-        self.ref = object
+    /// Create a TypedArray with the provided number of elements allocated. All the elements will be initialized to zero.
+    public init(length: Int) {
+        jsObject = Element.typedArrayClass.new(length)
     }
 
-    public convenience init(length: Int) {
-        let jsObject = Element.typedArrayClass.new(length)
-        self.init(unsafe: jsObject)
+    required public init(withCompatibleObject jsObject: JSObject) {
+        self.jsObject = jsObject
     }
 
     required public convenience init(arrayLiteral elements: Element...) {
         self.init(elements)
     }
 
+    /// Convert an array of numbers into a JavaScript TypedArray
     public convenience init(_ array: [Element]) {
         var resultObj = JavaScriptObjectRef()
         array.withUnsafeBufferPointer { ptr in
             _create_typed_array(Element.typedArrayKind, ptr.baseAddress!, Int32(array.count), &resultObj)
         }
-        self.init(unsafe: JSObject(id: resultObj))
+        self.init(withCompatibleObject: JSObject(id: resultObj))
     }
 
     public convenience init(_ stride: StrideTo<Element>) where Element: Strideable {

Sources/JavaScriptKit/FundamentalObjects/JSFunction.swift

@@ -43,10 +43,7 @@ public class JSFunction: JSObject {
                 let argv = bufferPointer.baseAddress
                 let argc = bufferPointer.count
                 var resultObj = JavaScriptObjectRef()
-                _call_new(
-                    self.id, argv, Int32(argc),
-                    &resultObj
-                )
+                _call_new(self.id, argv, Int32(argc), &resultObj)
                 return JSObject(id: resultObj)
             }
         }
@@ -57,6 +54,10 @@ public class JSFunction: JSObject {
         fatalError("unavailable")
     }
 
+    public override class func construct(from value: JSValue) -> Self? {
+        return value.function as? Self
+    }
+
     override public func jsValue() -> JSValue {
         .function(self)
     }
@@ -89,6 +90,15 @@ public class JSClosure: JSFunction {
         }
     }
 
+    public required convenience init(jsValue: JSValue) {
+        switch jsValue {
+        case let .function(fun):
+            self.init { fun(arguments: $0) }
+        default:
+            fatalError()
+        }
+    }
+
     public func release() {
         Self.sharedFunctions[hostFuncRef] = nil
         isReleased = true

Sources/JavaScriptKit/FundamentalObjects/JSObject.swift

@@ -8,13 +8,18 @@ public class JSObject: Equatable {
     }
 
     @_disfavoredOverload
-    public subscript(dynamicMember name: String) -> ((JSValueConvertible...) -> JSValue)? {
+    public subscript(_ name: String) -> ((JSValueConvertible...) -> JSValue)? {
         guard let function = self[name].function else { return nil }
         return { (arguments: JSValueConvertible...) in
             function(this: self, arguments: arguments)
         }
     }
 
+    @_disfavoredOverload
+    public subscript(dynamicMember name: String) -> ((JSValueConvertible...) -> JSValue)? {
+        self[name]
+    }
+
     public subscript(dynamicMember name: String) -> JSValue {
         get { self[name] }
         set { self[name] = newValue }
@@ -43,6 +48,10 @@ public class JSObject: Equatable {
         return lhs.id == rhs.id
     }
 
+    public class func construct(from value: JSValue) -> Self? {
+        return value.object as? Self
+    }
+
     public func jsValue() -> JSValue {
         .object(self)
     }

Sources/JavaScriptKit/JSBridgedType.swift

@@ -0,0 +1,41 @@
+/// Use this protocol when your type has no single JavaScript class.
+/// For example, a union type of multiple classes or primitive values.
+public protocol JSBridgedType: JSValueCodable, CustomStringConvertible {
+    /// This is the value your class wraps.
+    var value: JSValue { get }
+
+    /// If your class is incompatible with the provided value, return `nil`.
+    init?(from value: JSValue)
+}
+
+extension JSBridgedType {
+    public static func construct(from value: JSValue) -> Self? {
+        return Self.init(from: value)
+    }
+
+    public func jsValue() -> JSValue { value }
+
+    public var description: String { value.description }
+}
+
+/// Conform to this protocol when your Swift class wraps a JavaScript class.
+public protocol JSBridgedClass: JSBridgedType {
+    /// The constructor function for the JavaScript class
+    static var constructor: JSFunction { get }
+
+    /// The JavaScript object wrapped by this instance.
+    /// You may assume that `jsObject instanceof Self.constructor`
+    var jsObject: JSObject { get }
+
+    /// Create an instannce wrapping the given JavaScript object.
+    /// You may assume that `jsObject instanceof Self.constructor`
+    init(withCompatibleObject jsObject: JSObject)
+}
+
+extension JSBridgedClass {
+    public var value: JSValue { jsObject.jsValue() }
+    public init?(from value: JSValue) {
+        guard let object = value.object, object.isInstanceOf(Self.constructor) else { return nil }
+        self.init(withCompatibleObject: object)
+    }
+}