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iosswiftswift3javascriptcore

JSValue init(bool:in:) vs JSValueMakeBoolean()

I am playing around with the JavaScriptCore framework and have discovered two different ways to create booleans in a JavaScript context:

import JavaScriptCore

let context = JSContext()

let trueVal = JSValue(bool: true, in: context)
JSValueIsBoolean(context?.jsGlobalContextRef, trueVal?.jsValueRef) // true

let otherTrueValue = JSValueMakeBoolean(context?.jsGlobalContextRef, true)
JSValueIsBoolean(context?.jsGlobalContextRef, otherTrueValue) // true

What is the difference between JSValue(bool:in:) and JSValueMakeBoolean?

Solution

  • The generated header for JSValueRef keeps this comment:

     * Copyright (C) 2006 Apple Inc.  All rights reserved.

    And for JSValue:

     * Copyright (C) 2013 Apple Inc. All rights reserved.

    Seems JavaScriptCore framework was first developed for an old OS X (showing 10.5+ in the reference page) with C-function based APIs. And later it has come to iOS with a modern class based APIs.

    (Though, I have never used JavaScriptCore in such old OS X.)

    I haven't explored JavaScriptCore so deeply inside it, so I'm not sure such C-function based APIs still needed in some cases or not.

    But usually, you have no need to touch C-function APIs. For example, you can use isBoolean property rather than C-function JSValueIsBoolean.

    if let trueVal = JSValue(bool: true, in: context) {
    print(trueVal.isBoolean) //->true
}