at:tutorial:reflection
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at:tutorial:reflection [2008/09/15 17:58] – rewritten tvcutsem | at:tutorial:reflection [2010/11/16 15:59] – fixed tvcutsem | ||
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</ | </ | ||
- | The code excerpt presented above uses the mirror to // | + | The code excerpt presented above uses the mirror to // |
+ | |||
+ | {{: | ||
The code excerpt below shows how one can add and remove slots to and from an object, and how one can explicitly access values and invoke methods upon an object, reflectively: | The code excerpt below shows how one can add and remove slots to and from an object, and how one can explicitly access values and invoke methods upon an object, reflectively: | ||
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- | A complete overview of all meta-operations will be presented near the end of this chapter | + | A complete overview of all meta-operations will be presented near the end of this chapter. |
===== Mirages ===== | ===== Mirages ===== | ||
- | Extending the AmbientTalk core language | + | Extending the AmbientTalk core language |
As a simple example, we show how to trace all method calls made on an object. The first step is to define a //mirror// object that encapsulates this logging behaviour. A mirror object must implement the complete AmbientTalk MOP. To make it convenient to make small changes to the MOP, AmbientTalk provides the '' | As a simple example, we show how to trace all method calls made on an object. The first step is to define a //mirror// object that encapsulates this logging behaviour. A mirror object must implement the complete AmbientTalk MOP. To make it convenient to make small changes to the MOP, AmbientTalk provides the '' | ||
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< | < | ||
def createTracingMirror(baseObject) { | def createTracingMirror(baseObject) { | ||
- | extend: defaultMirror with: { | + | extend: defaultMirror.new(baseObject) |
def invoke(slf, invocation) { | def invoke(slf, invocation) { | ||
system.println(" | system.println(" | ||
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</ | </ | ||
- | The primitive '' | + | The primitive '' |
< | < | ||
- | def createTracingMirror(baseObject) { | + | def TracingMirror := mirror: { |
- | | + | def invoke(slf, invocation) { |
- | def invoke(slf, invocation) { | + | system.println(" |
- | system.println(" | + | super^invoke(slf, |
- | super^invoke(slf, | + | |
- | } | + | |
} | } | ||
} | } | ||
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In the code above, the closure passed to '' | In the code above, the closure passed to '' | ||
- | When invoking the method | + | Another alternative is to just pass a mirror prototype to '' |
< | < | ||
- | > mirage.m(); | + | def mirage := object: { |
- | invoked | + | def foo() { 42 }; |
+ | } mirroredBy: TracingMirror; | ||
+ | </ | ||
+ | |||
+ | The AmbientTalk VM will then call '' | ||
+ | |||
+ | When invoking the method '' | ||
+ | |||
+ | < | ||
+ | > mirage.foo(); | ||
+ | invoked | ||
>> 42 | >> 42 | ||
</ | </ | ||
+ | |||
+ | The picture below gives an overview of the different objects involved in the actor. | ||
+ | |||
+ | {{: | ||
Whereas the example provided above may seem a little contrived, the reflective capabilities of AmbientTalk allow it to be extended with many abstraction relating to distributed computing for mobile ad hoc networks (AmbientTalk' | Whereas the example provided above may seem a little contrived, the reflective capabilities of AmbientTalk allow it to be extended with many abstraction relating to distributed computing for mobile ad hoc networks (AmbientTalk' | ||
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===== The Metaobject Protocol ===== | ===== The Metaobject Protocol ===== | ||
- | The Meta-Object Protocol of AmbientTalk can be divided into a series of independent protocols. Whereas the full semantics and signature of the meta-methods can be found in the [[http://prog.vub.ac.be/ | + | The Meta-Object Protocol of AmbientTalk can be divided into a series of independent protocols. Whereas the full semantics and signature of the meta-methods can be found in the [[http://soft.vub.ac.be/ |
+ | |||
+ | The **Message Invocation Protocol** consists of methods to deal with both synchronous and asynchronous method invocation. It provides necessary hooks to intercept both the reception of asynchronous messages and the invocation of synchronous messages. Moreover, it provides a hook to intercept asynchronous messages being sent by the object, allowing the object to add additional metadata to the message. The '' | ||
- | The **Message Passing Protocol** consists of methods to deal with both synchronous and asynchronous message sending. It provides necessary hooks to intercept both the reception of asynchronous messages and the invocation of synchronous messages. Moreover, it provides a hook to intercept asynchronous messages being sent by the object, allowing the object to add additional metadata to the message. The '' | + | {{: |
- | The **Object | + | The **Object |
The **Slot Access and Modification Protocol** consists of operations which allow trapping both dynamic access and modification to slots. For instance, '' | The **Slot Access and Modification Protocol** consists of operations which allow trapping both dynamic access and modification to slots. For instance, '' | ||
- | The **Structural Access Protocol** consists of operations used list all available slots, get access to a first-class slot representation and to add new slots to an existing object. The '' | + | The **Structural Access Protocol** |
- | The **Instantiation Protocol** consists of the '' | + | The **Object |
The **Relational Testing Protocol** consists of the methods '' | The **Relational Testing Protocol** consists of the methods '' | ||
- | The **Type | + | The **Type |
The **Evaluation Protocol** ensures that any AmbientTalk object can be part of a parse tree, and therefore every object provides meaningful implementations of the '' | The **Evaluation Protocol** ensures that any AmbientTalk object can be part of a parse tree, and therefore every object provides meaningful implementations of the '' |
at/tutorial/reflection.txt · Last modified: 2010/11/16 16:32 by tvcutsem