Some links on the Delphi VolatileAttribute

August 2021
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This attribute feature is included in the new RTTI added in Delphi 2010, but there are some attributes that are predefined in RTL, although there are differences depending on the Delphi version. However, there is no descriptive description of these predefined attributes in the help. So I examined it (~~I have not checked out XE6 / XE7 because I do not have it at hand, but I don’t think there is any difference between XE5 and existing one~~(I also checked Delphi XE6 / XE7 / XE8 / 10 Seattle / 10.1 Berlin).

- System unit
  
  TCustomAttribute
  
  [2010..10.3 Rio] Root class of custom attribute To
  define a new attribute, derive from TCustomAttribute
  
  WeakAttribute [Weak]
  
  [XE3..10.3 Rio] Indicates a “weak” reference that prevents situations where ARC cannot destroy objects such as circular references
  10 Seattle and earlier NEXTGEN compiler only
  Reference: Compiler attributes-RAD Studio
  reference : Weak references (automatic reference counting with Delphi mobile compiler)
  
  UnsafeAttribute [Unsafe]
  
  [XE3..10.3 Rio] Prevents ARC destruction when the reference count is 0, such as when an object is created
  10 Seattle and earlier NEXTGEN compiler only
  Reference: Compiler attributes-RAD Studio
  Reference: Unsafe attribute (Delphi Mobile (Automatic reference counting by the compiler)
  Reference: Delphi language for mobile development (white paper)
  
  RefAttribute [Ref]
  
  [XE3..10.3 Rio] Force constant parameter to pass by reference
  According to help, RefAttribute is a new feature of XE4 , but it can actually be used in XE3.
  Reference: Compiler attribute-RAD Studio
  Reference: Constant parameter (Parameter ( Delphi))
  
  VolatileAttribute [Volatile]
  
  [XE4..10.3 Rio] Do not perform optimizations that copy values to registers or other temporary memory areas during code generation for fields that may be rewritten by threads
  10 Seattle and earlier NEXTGEN compiler only
  Reference: Compiler attributes-RAD Studio
  Reference: Delphi compiler new attributes (new in Delphi XE4 and C ++ Builder XE4)
  Reference: volatile (compiler attribute)
  
  StoredAttribute [Stored]
  
  [XE7..10.3 Rio] See System.Classes.StoredAttribute
  
  HPPGENAttribute [HPPGEN]
  
  [XE8..10.3 Rio] It seems to be information used when generating hpp file for C ++ Builder, but details are unknown
  
  HFAAttribute [HFA]
  
  [XE8..10.3 Rio]~~There seems to be information on pageId = 86770118 (what it), but details are unknown ( commented with For internal use only. )~~Override RTTI HFA information generated for record / array types for ARM64 platforms
  
  AlignAttribute [Align]
  
  [10 Seattle..10.3 Rio] It seems to specify the alignment of objects in memory, but there is a comment , For internal use only.

- System.Classes unit
  ComponentPlatformsAttribute [ComponentPlatforms(<params>)]
  [XE2..10.3 Rio] Specify the platform on which the component operates. Specify
  the logical sum of the following constants defined in System.Classes for the parameter (Word value).
  - pidWin32 [XE2..10.3 Rio]
  - pidWin64 [XE2..10.3 Rio]
  - pidOSX32 [XE2..10.3 Rio]
  - pidiOSSimulator32 [10.3 Rio], pidiOSSimulator [XE3..10.3 Rio]
  - pidAndroid32Arm [10.3 Rio], pidAndroid [XE3..10.3 Rio]
  - pidLinux32 [XE3..10.3 Rio]
  - pidiOSDevice32 [XE8..10.3 Rio], pidiOSDevice [XE3..10.3 Rio]
  - pidLinux64 [XE8..10.3 Rio]
  - pidWinNX32 [XE3..10.3 Rio]
  - pidWinIoT32 [XE8..10.3 Rio] (“Embedded IoT (Internet of Things) Windows w / Intel Galileo”)
  - pidiOSDevice64 [XE8..10.3 Rio]
  - pidWinARM32 [10.3 Rio], pidWinARM [10 Seattle..10.2 Tokyo]
  - pidOSX64 [10.1 Berlin..10.3 Rio], pidOSXNX64 [10.1 Berlin..10.2 Tokyo]
  - pidLinux32Arm [10.1 Berlin..10.3 Rio]
  - pidLinux64Arm [10.1 Berlin..10.3 Rio]
  - pidAndroid64Arm [10.3 Rio], pidAndroid64 [10.1 Berlin..10.2 Tokyo]
  - pidiOSSimulator64 [10.3 Rio]
  TDefaultAttributeBase
  
  [XE3..10.3 Rio] DefaultAttribute / NoDefaultAttribute inheritance source
  
  DefaultAttribute [Default(<param>)]
  
  [XE3..10.3 Rio] The property storage specifier default is equivalent
  to the default value (Boolean type, AnsiChar type, Char type, Integer type, Cardinal type, Int64 type, UInt64 type, String type, Extended type) Any)
  
  NoDefaultAttribute [NoDefault]
  
  [XE3..10.3 Rio] Property storage specifier equivalent to nodefault
  
  StoredAttribute [Stored(<param>)]
  
  [XE3..XE7] Specify the name of a boolean value (False | True) or storage handler (a method that returns a Boolean value without a Boolean property or parameter) for the specified parameter equivalent to the property storage specifier stored
  (Move to System unit after XE8)
  
  ObservableMemberAttribute [ObservableMember(<param>)]
  
  [XE3..10.3 Rio] In LiveBindings compatible component, specify the member name used by LiveBindings component when generating an expression as a parameter

- System.JSON.Serializers unit
  JsonConverterAttribute[JsonConverter<param>]
  
  [10.3 Rio] Specifying the converter used by TJsonSerializer
  
  JsonIgnoreAttribute[JsonIgnore]
  
  [10.3 Rio] Specifying members to be ignored by TJsonSerializer
  
  JsonNameAttribute[JsonName<param>]
  
  [10.3 Rio] Explicitly specify key name in TJsonSerializer
  
  JsonInAttribute[JsonIn]
  
  [10.3 Rio] When TJsonMemberSerialization.In is specified in the parameter of JsonSerialize attribute, it is serialized / deserialized with TJsonSerializer
  
  JsonObjectHandlingAttribute[JsonObjectHandling<param>]
  [10.3 Rio] Specify handling of class type members when deserializing with
  TJsonSerializer Specify one of the following values from enumeration type TJsonObjectHandling as a parameter
  - Auto [10.2 Tokyo..10.3 Rio]
  - Reuse [10.2 Tokyo..10.3 Rio]
  - Replace [10.2 Tokyo..10.3 Rio]
  JsonObjectOwnership[JsonObjectOwnership<param>]
  [10.3 Rio] Specify handling of original instance when class type member is generated when deserializing with
  TJsonSerializer Specify one of the following values from enumeration type TJsonObjectOwnership for parameter
  - Auto [10.2 Tokyo..10.3 Rio]
  - Owned [10.2 Tokyo..10.3 Rio]
  - NotOwned [10.2 Tokyo..10.3 Rio]
  JsonSerializeAttribute[JsonSerialize<param>]
  [10.2 Tokyo..10.3 Rio] Specifying the member to be serialized / deserialized with
  TJsonSerializer Specify one of the following values from enumeration type TJsonMemberSerialization for the parameter
  - Fields [10.2 Tokyo..10.3 Rio]
  - Public [10.2 Tokyo..10.3 Rio]
  - In [10.2 Tokyo..10.3 Rio]

- Data.DBXJSONReflectUnit ( REST.JsonReflectreplaced with unit in XE5 )
  
  JsonReflect [JsonReflect(<params>)]
  
  [XE..10.3 Rio] TJSONMarshal / TJSONUnMarshal
  parameters for customizing the behavior when marshalling / unmarshalling objects in JSON format include converter type, reverter type, interceptor type, population customizer type, marshalling Specifies whether to automatically release generated intermediate objects
  
  JSONBooleanAttribute
  
  [XE..10.3 Rio] Inheritance of JSONMarshalled / JSONOwned
  
  JSONMarshalled [JSONMarshalled(<param>)]
  
  [XE..10.3 Rio] Use parameter (False | True) to specify whether the field or type is subject to marshalling / unmarshalling
  
  JSONOwned [JSONOwned(<param>)]
  
  [XE..10.3 Rio] Specify with parameter (False | True) whether to release the field during unmarshalling

- Datasnap.DSAuth unit
  
  TRoleAuth [TRoleAuth(<params>)]
  
  [XE..10.3 Rio] When authenticating with DataSnap, specify the role to allow / deny access to the server method class and server method Specify
  the list of allowed roles and the list of denied roles as parameters
  Reference: Role (authentication and authorization)

- REST.Json.Types unit
  
  JSONBooleanAttribute [JSONBoolean]
  
  [XE6..10.3 Rio] See Data.DBXJSONReflect.JSONBooleanAttribute
  
  JSONMarshalledAttribute [JSONMarshalled]
  
  [XE6..10.3 Rio] See Data.DBXJSONReflect.JSONMarshalled
  
  JSONOwnedAttribute [JSONOwned]
  
  [XE6..10.3 Rio] See Data.DBXJSONReflect.JSONOwned
  
  JSONNameAttribute [JSONName]
  
  [XE6..10.3 Rio]

- REST.JsonReflect unit
  
  JsonReflect(XE5)/JsonReflectAttribute(XE6以降) [JsonReflect]
  
  [XE5..10.3 Rio] Refer to Data.DBXJSONReflect.JsonReflect (class name changed in XE6)
  
  JSONBooleanAttribute [JSONBoolean]
  
  [XE5] Refer to Data.DBXJSONReflect.JSONBooleanAttribute (Move to REST.Json.Types unit after XE6)
  
  JSONMarshalled [JSONMarshalled]
  
  [XE5] Refer to Data.DBXJSONReflect.JSONMarshalled (Move to REST.Json.Types unit after XE6)
  
  JSONOwned [JSONOwned]
  
  [XE5] Refer to Data.DBXJSONReflect.JSONOwned (Move to REST.Json.Types unit after XE6)

- EMS.ResourceType unit
  
  TResourceCustomAttribute [TResourceCustom]
  
  [10.1 Berlin..10.3 Rio] EndPointRequestSummaryAttribute (10.1 Berlin..10.2 Tokyo) / EndPointRequestParameterAttribute (10.1 Berlin..10.2 Tokyo) / EndPointResponseDetailsAttribute (10.1 Berlin..10.2 Tokyo) / EndPointObjectsYAMLDefinitionsAttribute (10.1 Berlin..10.2 Tokyo) / EndPointObjectsJSONDefinitionsAttribute ( 10.1 Berlin..10.3 Rio) / AllowAnonymousTenantAttribute (10.1 Berlin..10.2 Tokyo) / ResourceNameAttribute (10.3 Rio) / EndPointObjectsYAMLDefinitionsAttribute (10.3 Rio)
  
  TEndpointCustomAttribute [TEndpointCustom]
  
  [10.3 Rio] ResourceSuffixAttribute / EndpointNameAttribute / EndPointRequestSummaryAttribute / EndPointRequestParameterAttribute / EndPointResponseDetailsAttribute / AllowAnonymousTenantAttribute / EndPointProduceAttribute / EndPointMethodAttribute inheritance source
  
  ResourceSuffixAttribute [ResourceSuffix]
  
  [XE7..10.3 Rio] Specify URL suffix with EMS
  Reference: Overview of EMS resources-RAD Studio
  
  ResourceNameAttribute [ResourceName]
  
  [XE7..10.3 Rio] Specify resource name in EMS
  Reference: EMS Resource Overview-RAD Studio
  
  EndpointNameAttribute [EndpointName]
  
  [XE7..10.3 Rio] Specify endpoint method name in EMS
  Reference: Overview of EMS resources-RAD Studio
  
  EndPointRequestSummaryAttribute [EndPointRequestSummary]
  
  [10.1 Berlin..10.3 Rio] Generate method description on API document with EMS
  Reference: Custom API document-RAD Studio
  
  EndPointRequestParameterAttribute [EndPointRequestParameter]
  
  [10.1 Berlin..10.3 Rio] Generate description of parameters used in request in EMS on API document
  Reference: Custom API document-RAD Studio
  
  EndPointResponseDetailsAttribute [EndPointResponseDetails]
  
  [10.1 Berlin..10.3 Rio] Generate request response description on API document with EMS
  Reference: Custom API document-RAD Studio
  
  EndPointObjectsYAMLDefinitionsAttribute [EndPointObjectsYAMLDefinitions]
  
  [10.1 Berlin..10.3 Rio] Generate YAML version object definition on API document with EMS
  Reference: Custom API document-RAD Studio
  
  EndPointObjectsJSONDefinitionsAttribute [EndPointObjectsJSONDefinitions]
  
  [10.1 Berlin..10.3 Rio] Generate JSON object definition on API document with EMS
  Reference: Custom API document-RAD Studio
  
  AllowAnonymousTenantAttribute [AllowAnonymousTenant]
  
  [10.2 Tokyo..10.3 Rio] Skip the tenant verification procedure in EMS
  Reference: Sample RAD server Multi-tenant application-RAD Studio
  
  EndPointProduceAttribute
  
  [10.3 Rio]
  Reference: RAD Server extension URL mapping-RAD Studio
  
  EndPointConsumeAttribute
  
  [10.3 Rio]
  Reference: RAD Server extension URL mapping-RAD Studio

- Macapi.ObjectiveC unit
  
  MethodNameAttribute [MethodName]
  
  [XE4..10.3 Rio] Specify the original method name on Objective-C for Objective-C method defined in Delphi

- Androidapi.JNIBridge unit
  
  JavaSignatureAttribute [JavaSignature]
  
  [XE5..10.3 Rio] Specify the original class name on Android for Android (JNI) class (interface) defined in Delphi

System.Win.WinRT unit

WinRTClassNameAttribute [WinRTClassName]

[10 Seattle..10.3 Rio] Specify the original class name on WinRT for the WinRT API interface defined in Delphi

Differences between Delphi versions:

In Delphi 2010 there are no predefined attributes to use in the system.
Delphi XE defined TRoleAuth for DataSnap and JSON … for JSON reflection for DBX.
Delphi XE2 defines ComponentPlatformsAttribute for multi-platform support.
Delphi XE3 defined WeakAttribute / UnsafeAttribute / RefAttribute for ARC, possibly TDefaultAttributeBase / DefaultAttribute / NoDefaultAttribute / StoredAttribute for the transition from the old RTTI to the new RTTI, and ObservableMemberAttribute for LiveBinding.
In Delphi XE4, MethodNameAttribute is defined for iOS.
In Delphi XE5, JSON reflection is separated from DBX, so Data.DBXJSONReflect’s JSON … is redefined in REST.JsonReflect, and JavaSignatureAttribute is defined for Android.
In Delphi XE6, the class name of REST.JsonReflect.JsonReflect has been changed to REST.JsonReflect.JsonReflectAttribute, and the definition of Json … other than JsonReflectAttribute has been moved from the REST.JsonReflect unit to the REST.Json.Types unit.
Delphi XE7 moved the StoredAttribute definition from the System.Classes unit to the System unit, and defined ResourceSuffixAttribute / ResourceNameAttribute / EndpointNameAttribute for EMS.
Delphi XE8 defined HPPGENAttribute and HFAAttribute.
In Delphi 10 Seattle, AlignAttribute and WinRTClassNameAttribute were defined.
Delphi 10.1 Berlin now supports the [weak] [unsafe] [volatile] attribute for all compilers (only NEXTGEN compiler before 10 Seattle). In addition , TResourceCustomAttribute / EndPointRequestSummaryAttribute / EndPointRequestParameterAttribute / EndPointResponseDetailsAttribute / EndPointObjectsYAMLDefinitionsAttribute / EndPointObjectsJSONDefinitionsAttribute for custom API document used for EMS API resource acquisition was defined.
In Delphi 10.2 Tokyo, the System.JSON.Serializers unit was added to define JSON serialization-related Json …, and AllowAnonymousTenantAttribute was defined to support EMS multi-tenancy. The System.JSON.Serializers unit is not officially documented at the moment (2017/04/10), so changes that are unlikely to be written in Lyna ‘s Delphi 10.2 Tokyo docwiki. – Zenryokuwawa , use of TJsonSerializer. – Zenryokuwawa , practical examples of TJsonSerializer – Zenryokuwawa See the per.
In Delphi 10.3 Rio, the inheritance relationship of attribute classes on the EMS.ResourceTypes unit has been rearranged.

If you want to specify an attribute for the return value of a method, such as the Unsafe attribute, [Result: <attr>]add a prefix before the method declaration ,

[Result: Unsafe]function Foo: TObject;

Like this.

2015/06/19 update: Added information about Delphi XE6 / XE7 / XE8.

2015/10/05 update: Added information about Delphi 10 Seattle.

2016/05/02 postscript: Added information about Delphi 10.1 Berlin.

2017/04/10 postscript: Added information about Delphi 10.2 Tokyo. I quoted a lot from Lyna . Thank you very much.

2019/03/07 update: Added information about Delphi 10.3 Rio.

Delphi

VolatileAttribute = class(TCustomAttribute);

Properties

Type	Visibility	Source	Unit	Parent
class	public	System.pas	System	System

Description

TCustomAttribute is the base class for all Delphi attributes.

System.VolatileAttribute inherits from System.TCustomAttribute. All content below this line refers to System.TCustomAttribute.

TCustomAttribute is the base class for all Delphi attributes.

Declare descendants of TCustomAttribute to later use them as attributes in Delphi code. An attribute is a special kind of class that can be annotated to any type or member in Delphi.

Code Examples

AttributesAndRTTI Sample[WayBack] System.VolatileAttribute – RAD Studio API Documentation

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