API/JSManagedValue.h

   1 /*
   2  * Copyright (C) 2013 Apple Inc. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
  14  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  15  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
  17  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  18  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  19  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  20  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  21  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  22  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
  23  * THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #ifndef JSManagedValue_h
  27 #define JSManagedValue_h
  28
  29 #import <JavaScriptCore/JSBase.h>
  30
  31 #if JSC_OBJC_API_ENABLED
  32
  33 @class JSValue;
  34 @class JSContext;
  35
  36 // JSManagedValue represents a "conditionally retained" JSValue.
  37 // "Conditionally retained" means that as long as either the JSManagedValue
  38 // JavaScript value is reachable through the JavaScript object graph
  39 // or the JSManagedValue object is reachable through the external Objective-C
  40 // object graph as reported to the JSVirtualMachine using
  41 // addManagedReference:withOwner:, the corresponding JavaScript value will
  42 // be retained. However, if neither of these conditions are true, the
  43 // corresponding JSValue will be released and set to nil.
  44 //
  45 // The primary use case for JSManagedValue is for safely referencing JSValues
  46 // from the Objective-C heap. It is incorrect to store a JSValue into an
  47 // Objective-C heap object, as this can very easily create a reference cycle,
  48 // keeping the entire JSContext alive.
  49 NS_CLASS_AVAILABLE(10_9, 7_0)
  50 @interface JSManagedValue : NSObject
  51
  52 // Convenience method for creating JSManagedValues from JSValues.
  53 + (JSManagedValue *)managedValueWithValue:(JSValue *)value;
  54
  55 // Create a JSManagedValue.
  56 - (id)initWithValue:(JSValue *)value;
  57
  58 // Get the JSValue to which this JSManagedValue refers. If the JavaScript value has been collected,
  59 // this method returns nil.
  60 - (JSValue *)value;
  61
  62 @end
  63
  64 #endif // JSC_OBJC_API_ENABLED
  65
  66 #endif // JSManagedValue_h