at:tutorial:objects
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at:tutorial:objects [2007/06/29 13:31] – jorge | at:tutorial:objects [2007/07/02 13:34] – jorge | ||
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Every object understands the message '' | Every object understands the message '' | ||
+ | |||
+ | AmbientTalk also provides a '' | ||
+ | |||
+ | < | ||
+ | > def clonedPoint := clone: point | ||
+ | </ | ||
===== Delegation and cloning ===== | ===== 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 child-parent relationship. We identify two kinds of delegation relationships: | + | 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 57: | 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 68: | 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 |
} | } | ||
} | } | ||
Line 75: | Line 85: | ||
===== Delegation and dynamic inheritance ===== | ===== Delegation and dynamic inheritance ===== | ||
- | An object' | + | The parent |
+ | < | ||
+ | > def openConnection := object: {...}; | ||
+ | def closedConnection := object: {...}; | ||
+ | def connection := object: { | ||
+ | def open() { | ||
+ | super := openConnection.new(); | ||
+ | }; | ||
+ | def close() { | ||
+ | super := closedConnection.new(); | ||
+ | }; | ||
+ | } | ||
+ | </ | ||
- | ===== First-class | + | ===== 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