at:tutorial:reflection
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at:tutorial:reflection [2007/07/23 15:51] – elisag | at:tutorial:reflection [2008/09/15 17:26] – * tvcutsem | ||
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- | < | ||
- | |||
====== Reflective Programming ====== | ====== Reflective Programming ====== | ||
[[wp> | [[wp> | ||
- | The reflective model of AmbientTalk is based on [[http:// | + | The reflective model of AmbientTalk is based on [[http:// |
===== Mirrors ===== | ===== Mirrors ===== | ||
- | AmbientTalk uses a mirror-based architecture to provide reflective access to its objects. The basic principle of a mirror-based architecture is that all reflective facilities are encapsulated in a mirror object which provides reflective access to precisely one object, its reflectee. Moreover, the mirror of the object is not directly accessible as a slot of the object. Instead, a separate factory must be used to create mirrors, which allows the program to hand out different mirrors | + | |
+ | As we have mentioned in the introduction, | ||
+ | |||
+ | A convenience primitive exists that allows AmbientTalk programmers to acquire a mirror on an object without explicitly having to consult the mirror | ||
+ | |||
+ | Once a mirror has been created, it can be used to inspect | ||
< | < | ||
- | def baseObject | + | def Point := object: { |
- | def field := nil; | + | def x := 0; |
- | def canonicalMethod() { nil }; | + | def y := 0; |
- | def keyworded: arg1 method: arg2 { nil }; | + | def distanceToOrigin() |
}; | }; | ||
- | def mirror := reflect: | + | def p := Point.new(2, |
- | def slots := mirror.listSlots(); | + | // request a mirror |
- | slots.each: { | slot | system.println(slot) }; | + | > def mirrorOnP |
+ | >>< | ||
+ | |||
+ | > | ||
+ | >> | ||
</ | </ | ||
- | The code excerpt presented above uses the mirror to // | + | The code excerpt presented above uses the mirror to // |
- | In addition to allowing a program to reason about the structure of its objects, mirrors can also be used to write operations such as message sending | + | < |
+ | >def inspectable := object: { | ||
+ | def map(arg1, @restArgs) { restArgs.map(arg1); | ||
+ | >>< | ||
+ | >def mirrorOnInspectable := reflect: inspectable; | ||
+ | >>< | ||
+ | > | ||
+ | >> | ||
+ | > | ||
+ | >> | ||
+ | < | ||
+ | >def method := mirrorOnInspectable.grabMethod(`map); | ||
+ | >>< | ||
+ | > | ||
+ | >> | ||
+ | </ | ||
+ | |||
+ | Using a mirror on an object, it is possible to get access to a representation of the object' | ||
+ | |||
+ | In addition to allowing a program to reason about the structure of its objects, mirrors can also be used to perform | ||
< | < | ||
- | def invokeUserMethod(object) { | + | >def isTestMethod(meth) { |
- | def userInput | + | (meth.name.text ~= " |
- | // This example assumes that the user typed a single symbol | + | { meth.parameters |
- | (reflect: | + | >>< |
- | }; | + | >def retainTestMethods(obj) { |
+ | (reflect: obj).listMethods() | ||
+ | | ||
+ | >>< | ||
+ | >def runTest(obj) { | ||
+ | | ||
+ | (reflect: | ||
+ | >>< | ||
+ | > | ||
+ | ok | ||
+ | >>nil | ||
</ | </ | ||
Line 54: | Line 90: | ||
</ | </ | ||
- | < | + | < |
This mirror overrides the default implementation of the meta-operation '' | This mirror overrides the default implementation of the meta-operation '' | ||
Line 80: | Line 116: | ||
The **Object Passing Protocol** consists of two methods '' | The **Object Passing Protocol** consists of two methods '' | ||
- | The **Slot Access and Modification Protocol** consists of operations which allow trapping both access and modification to slots. These operations are further refined based on whether they transitively search the dynamic or lexical parent chain. For instance, | + | The **Slot Access and Modification Protocol** consists of operations which allow trapping both dynamic |
- | 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** 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 **Instantiation Protocol** consists of the '' | The **Instantiation Protocol** consists of the '' |
at/tutorial/reflection.txt · Last modified: 2010/11/16 16:32 by tvcutsem