at:tutorial:objects
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at:tutorial:objects [2007/06/29 13:21] – jorge | at:tutorial:objects [2007/07/02 13:44] – jorge | ||
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Every object understands the message '' | Every object understands the message '' | ||
- | ===== Delegation and Dynamic Inheritance | + | AmbientTalk also provides a '' |
- | AmbientTalk features object inheritance or delegation. By means of delegation, an object can reuse and extend the defintion of another establishing a child-parent relationship. We identify two kinds of delegation relationships: | + | |
- | These relationships define two different semantics for clonning child objects. Whereas clonning a **IS-A** child also clones its parent, **SHARE-A** child shares the parent of the cloned object. | + | < |
+ | > def clonedPoint := clone: point | ||
+ | </ | ||
+ | |||
+ | ===== Delegation and cloning | ||
+ | AmbientTalk features object inheritance or delegation. By means of delegation, an object can reuse and extend the defintion of another establishing a parent-child | ||
+ | |||
+ | |||
+ | {{: | ||
The following code shows how to extend objects with a **IS-A** relationship. It uses the '' | The following code shows how to extend objects with a **IS-A** relationship. It uses the '' | ||
Line 58: | Line 67: | ||
> def point3D := extend: point with: { | > def point3D := extend: point with: { | ||
def z := 0; | def z := 0; | ||
- | def sumofsquares() { | + | def sumOfSquares() { |
- | super.sumofsquares() + z*z | + | super^sumOfSquares() + z*z |
} | } | ||
} | } | ||
Line 69: | Line 78: | ||
> def point3D := share: point with: { | > def point3D := share: point with: { | ||
def z := 0; | def z := 0; | ||
- | def sumofsquares() { | + | def sumOfSquares() { |
- | super.sumofsquares() + z*z | + | super^sumOfSquares() + z*z |
} | } | ||
} | } | ||
</ | </ | ||
+ | ===== Delegation and dynamic inheritance ===== | ||
+ | The parent of an object is bound to a field named '' | ||
- | ===== Delegation and cloning ===== | + | < |
+ | > def openConnection := object: {...}; | ||
+ | > def closedConnection := object: {...}; | ||
+ | > def connection := object: { | ||
+ | def open() { | ||
+ | super := openConnection.new(); | ||
+ | }; | ||
+ | def close() { | ||
+ | super := closedConnection.new(); | ||
+ | }; | ||
+ | } | ||
+ | </ | ||
- | ===== First-class | + | <note important> |
+ | In AmbientTalk, | ||
+ | </ | ||
+ | |||
+ | ===== First-class | ||
+ | AmbientTalk provides an explicit delegation operator '' | ||
+ | |||
+ | < | ||
+ | > def point3D := extend: point with: { | ||
+ | def z := 0; | ||
+ | def init(aX, aY, aZ) { | ||
+ | super^init(aX, | ||
+ | z := aZ; | ||
+ | }; | ||
+ | } | ||
+ | </ | ||
+ | |||
+ | A message sent to an object using this symbol (e.g. to the parent object in the example above) will first look for the method that matches the selector indicated in the message in this object (and its parents) and then execute the method body in the lexical scope of the message sender. | ||
===== Encapsulation ===== | ===== Encapsulation ===== | ||
+ | In AmbientTalk, | ||
+ | < | ||
+ | > def makeObject(hidden) { | ||
+ | object: { | ||
+ | def foo() { /* use hidden */ } | ||
+ | } | ||
+ | } | ||
+ | </ | ||
+ | |||
+ | Due to the encapsulation of this object the following instruction fails: | ||
+ | |||
+ | < | ||
+ | > makeObject(5).hidden; | ||
+ | >> | ||
+ | < | ||
+ | </ |
at/tutorial/objects.txt · Last modified: 2013/05/17 20:23 by tvcutsem