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 #import <JavaScriptCore/WebKitAvailability.h>
  31
  32 #if JSC_OBJC_API_ENABLED
  33
  34 @class JSValue;
  35 @class JSContext;
  36
  37 /*!
  38 @interface
  39 @discussion JSManagedValue represents a "conditionally retained" JSValue.
  40  "Conditionally retained" means that as long as either the JSManagedValue's
  41  JavaScript value is reachable through the JavaScript object graph
  42  or the JSManagedValue object is reachable through the external Objective-C
  43  object graph as reported to the JSVirtualMachine using
  44  addManagedReference:withOwner:, the corresponding JavaScript value will
  45  be retained. However, if neither of these conditions are true, the
  46  corresponding JSValue will be released and set to nil.
  47
  48  The primary use case for JSManagedValue is for safely referencing JSValues
  49  from the Objective-C heap. It is incorrect to store a JSValue into an
  50  Objective-C heap object, as this can very easily create a reference cycle,
  51  keeping the entire JSContext alive.
  52 */
  53 #ifndef JSC_OBJC_API_AVAILABLE_MAC_OS_X_1080
  54 NS_CLASS_AVAILABLE(10_9, 7_0)
  55 #else
  56 OBJC_VISIBLE
  57 #endif
  58 @interface JSManagedValue : NSObject
  59
  60 /*!
  61 @method
  62 @abstract Create a JSManagedValue from a JSValue.
  63 @param value
  64 @result The new JSManagedValue.
  65 */
  66 + (JSManagedValue *)managedValueWithValue:(JSValue *)value;
  67 + (JSManagedValue *)managedValueWithValue:(JSValue *)value andOwner:(id)owner NS_AVAILABLE(10_10, 8_0);
  68
  69 /*!
  70 @method
  71 @abstract Create a JSManagedValue.
  72 @param value
  73 @result The new JSManagedValue.
  74 */
  75 - (instancetype)initWithValue:(JSValue *)value;
  76
  77 /*!
  78 @property
  79 @abstract Get the JSValue from the JSManagedValue.
  80 @result The corresponding JSValue for this JSManagedValue or
  81  nil if the JSValue has been collected.
  82 */
  83 @property (readonly, strong) JSValue *value;
  84
  85 @end
  86
  87 #endif // JSC_OBJC_API_ENABLED
  88
  89 #endif // JSManagedValue_h