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Commit b9b0977

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removed Fluent Interface Pattern and Monostate; refactored Memento and Observer design patterns
1 parent 1778d54 commit b9b0977

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8 files changed

+55
-168
lines changed

8 files changed

+55
-168
lines changed

‎src/main/kotlin/design_patterns/Fluent Interface Pattern.kt

Lines changed: 0 additions & 37 deletions
This file was deleted.

‎src/main/kotlin/design_patterns/Memento.kt

Lines changed: 19 additions & 19 deletions
Original file line numberDiff line numberDiff line change
@@ -2,50 +2,50 @@ package design_patterns
22

33
/**
44
*
5-
* pattern: Memento
5+
* Memento is a behavioral design pattern that allows without violating encapsulation to capture
66
*
7-
* allows without violating encapsulation, to fix and save the state of an object
8-
* in such a way as to restore it to this state
7+
* and save the internal state of an object so that it can be restored to this state later
98
*
109
*/
1110

1211

1312
class Bundle(val str: String)
1413

15-
/**
16-
* Android system emulating
17-
*/
14+
// Android system saves the application state in special bundles
15+
// I gave this as an example, Android system’s saving mechanism is much more complicated
1816
class AndroidSystem {
19-
private var bundle: Bundle = Bundle("")
17+
18+
private var savedBundle: Bundle = Bundle("")
2019

2120
fun saveBundle(bundle: Bundle) {
22-
this.bundle = bundle
21+
savedBundle = bundle
2322
}
2423

25-
fun restoreBundle() = bundle
24+
fun restoreBundle() = savedBundle
2625
}
2726

28-
/**
29-
* TextView is an Android component that draws text on the screen
30-
*/
31-
class TextView1 {
32-
private var text: String = ""
27+
// TextView is an Android component that draws text on the screen
28+
class TextView {
29+
30+
private var currentText: String = ""
3331

3432
fun setText(text: String) {
35-
this.text = text
33+
currentText = text
3634
}
3735

38-
fun text() = text
36+
fun text() = currentText
3937

4038
fun draw() {
41-
println(text)
39+
println(currentText)
4240
}
4341

42+
// saves the current state of TextView before re-creating it
4443
fun onSaveInstanceState(): Bundle {
45-
return Bundle(text)
44+
return Bundle(currentText)
4645
}
4746

47+
// restores the current state after TextView is recreated
4848
fun onRestoreInstanceState(bundle: Bundle) {
49-
text = bundle.str
49+
currentText = bundle.str
5050
}
5151
}

‎src/main/kotlin/design_patterns/Monostate.kt

Lines changed: 0 additions & 34 deletions
This file was deleted.

‎src/main/kotlin/design_patterns/Observer.kt

Lines changed: 12 additions & 20 deletions
Original file line numberDiff line numberDiff line change
@@ -2,48 +2,40 @@ package design_patterns
22

33
/**
44
*
5-
* pattern: Observer
5+
* Observer is is a behavioral design pattern that defines a one-to-many relationship between objects
66
*
7-
* using: used when we need to subscribe to changes of some object
8-
*
9-
* description: the object communicates its changes to observers
10-
* who previously subscribed to its changes
7+
* such that when the state of one object changes all dependent objects are automatically notified and updated
118
*
129
*/
1310

14-
fun interface Observer {
11+
fun interface PonyObserver {
1512
fun update(item: List<String>)
1613
}
1714

18-
/**
19-
* the interface of the object whose changes we will listen to
20-
*/
21-
interface Observable {
22-
fun observe(observer: Observer)
23-
fun cancel(observer: Observer)
15+
interface PonyObservable {
16+
fun addObserver(observer: PonyObserver)
17+
fun removeObserver(observer: PonyObserver)
2418
fun notifyObservers()
2519
}
2620

27-
/**
28-
* contains some data, when it changes we will notify observers
29-
*/
30-
class PonyList : Observable {
21+
// PonyList contains some data and when it changes we will notify observers
22+
class PonyList : PonyObservable {
3123

3224
private val ponies = mutableListOf<String>()
3325

34-
private val observers = mutableSetOf<Observer>()
26+
private val observers = mutableSetOf<PonyObserver>()
3527

3628
fun add(pony: String) {
3729
ponies.add(pony)
38-
// notify our observers that the data has changed
30+
// notify observers that the data has changed
3931
notifyObservers()
4032
}
4133

42-
override fun observe(observer: Observer) {
34+
override fun addObserver(observer: PonyObserver) {
4335
observers.add(observer)
4436
}
4537

46-
override fun cancel(observer: Observer) {
38+
override fun removeObserver(observer: PonyObserver) {
4739
observers.remove(observer)
4840
}
4941

‎src/test/kotlin/design_patterns/FluentInterfaceTest.kt

Lines changed: 0 additions & 20 deletions
This file was deleted.

‎src/test/kotlin/design_patterns/MementoTest.kt

Lines changed: 10 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -10,25 +10,23 @@ class MementoTest {
1010
// start Android system
1111
val androidOS = AndroidSystem()
1212

13-
val greetingText = TextView1()
14-
greetingText.setText(greeting)
15-
greetingText.draw()
13+
val greetingText = "Hello, World!"
14+
val greetingView = TextView()
15+
greetingView.setText(greetingText)
16+
greetingView.draw()
1617

1718
// rotating Android device (recreating application components)
18-
// saving state
19-
androidOS.saveBundle(greetingText.onSaveInstanceState())
19+
// Android system saves the states of running applications
20+
androidOS.saveBundle(greetingView.onSaveInstanceState())
2021

2122
// the state of the text was lost, but we saved it
22-
greetingText.setText("")
23+
greetingView.setText("")
2324

2425
// Android device has already rotated
25-
// restoring state
26-
greetingText.onRestoreInstanceState(androidOS.restoreBundle())
26+
// The system restores the states of running applications
27+
greetingView.onRestoreInstanceState(androidOS.restoreBundle())
2728

28-
assertEquals(greeting, greetingText.text())
29+
assertEquals(greetingText, greetingView.text())
2930
}
3031

31-
companion object {
32-
private const val greeting = "Hello, World!"
33-
}
3432
}

‎src/test/kotlin/design_patterns/MonostateTest.kt

Lines changed: 0 additions & 24 deletions
This file was deleted.

‎src/test/kotlin/design_patterns/ObserverTest.kt

Lines changed: 14 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -8,10 +8,22 @@ internal class ObserverTest {
88
@Test
99
fun test() {
1010
val ponyList = PonyList()
11-
ponyList.observe { items ->
12-
assertEquals("Twillight Sparkle", items.first())
11+
12+
val observer1 = PonyObserver { items ->
13+
assertEquals(listOf("Twillight Sparkle"), items)
1314
}
15+
ponyList.addObserver(observer1)
16+
// we add the first item, observer1 is triggered
1417
ponyList.add("Twillight Sparkle")
18+
// we remove observer1 so that it is not called again
19+
ponyList.removeObserver(observer1)
20+
21+
val observer2 = PonyObserver { items ->
22+
assertEquals(listOf("Twillight Sparkle", "Starlight Glimmer"), items)
23+
}
24+
ponyList.addObserver(observer2)
25+
// we add the second item, observer2 is triggered
26+
ponyList.add("Starlight Glimmer")
1527
}
1628

1729
}

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