at:tutorial:objects
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at:tutorial:objects [2007/06/27 14:08] – jorge | at:tutorial:objects [2007/07/03 09:57] – jorge | ||
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< | < | ||
- | > def Point := object: { | + | > def point := object: { |
def x := 0; | def x := 0; | ||
def y := 0; | def y := 0; | ||
- | def init(xCoord,yCoord) { | + | def init(aX,aY) { |
- | x := xCoord; | + | x := aX; |
- | y := yCoord; | + | y := aY; |
}; | }; | ||
def sumOfSquares() { x*x + y*y }; | def sumOfSquares() { x*x + y*y }; | ||
} | } | ||
- | >>< | ||
</ | </ | ||
- | As all definitions in AmbientTalk, | + | As all definitions in AmbientTalk, |
- | This object can be instantiated to create new points as follows: | + | |
- | <code> | + | <note important> |
- | > def aPoint := Point.new(2,3) | + | AmbientTalk not only supports traditional canonical syntax (e.g. '' |
- | >>< | + | </note> |
- | </code> | + | |
- | Every object understands | + | In the example above, the state of the '' |
===== Sending messages ===== | ===== Sending messages ===== | ||
- | In AmbientTalk, | + | In AmbientTalk, |
- | + | ||
- | Object' | + | |
< | < | ||
- | > aPoint.x | + | > point.x |
>>2 | >>2 | ||
- | > aPoint.sumOfSquares() | + | > point.sumOfSquares() |
>>13 | >>13 | ||
</ | </ | ||
- | <note important> | + | This code shows two messages sent to the '' |
- | Note that AmbientTalk supports both traditional canonical syntax (e.g. o.m(a, | + | |
- | </ | + | |
===== Cloning and instantiation ===== | ===== Cloning and instantiation ===== | ||
+ | As said before in this section, AmbientTalk objects are created [[objects# | ||
+ | < | ||
+ | > def anotherPoint := point.new(2, | ||
+ | </ | ||
+ | Every object understands the message '' | ||
- | ===== Delegation | + | 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 parent-child relationship. We identify two kinds of delegation relationships: | ||
- | ===== First-class | + | |
+ | {{: | ||
+ | |||
+ | |||
+ | The following code shows how to extend objects with a **IS-A** relationship. It uses the '' | ||
+ | |||
+ | < | ||
+ | > def point3D := extend: point with: { | ||
+ | def z := 0; | ||
+ | def sumOfSquares() { | ||
+ | super^sumOfSquares() + z*z | ||
+ | } | ||
+ | } | ||
+ | </ | ||
+ | |||
+ | The following code shows how to extend objects with a **SHARE-A** relationship. It uses the '' | ||
+ | |||
+ | < | ||
+ | > def point3D := share: point with: { | ||
+ | def z := 0; | ||
+ | def sumOfSquares() { | ||
+ | super^sumOfSquares() + z*z | ||
+ | } | ||
+ | } | ||
+ | </ | ||
+ | |||
+ | ===== Delegation and dynamic inheritance ===== | ||
+ | The parent of an object is bound to a field named '' | ||
+ | |||
+ | < | ||
+ | > def openConnection := object: {...}; | ||
+ | > def closedConnection := object: {...}; | ||
+ | > def connection := object: { | ||
+ | def open() { | ||
+ | super := openConnection.new(); | ||
+ | }; | ||
+ | def close() { | ||
+ | super := closedConnection.new(); | ||
+ | }; | ||
+ | } | ||
+ | </ | ||
+ | |||
+ | <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 the '' | ||
===== 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