介紹

昨天太趕，跟本沒時間好好理解

合成模式由三個部件組成

1. Component：抽象層，提供介面定義行為
2. Composite：樹支，擁有樹葉
3. Leaf：樹葉，結構最末端

依照做法還有分

1. 安全式合成模式：樹支定義管理方法
2. 透明式合成模式：抽象層定義管理方法

合成模式實作

1. 建立 Component 抽象層

/**
 * Component：抽象層，提供介面定義行為
 */
abstract class Component(var name: String) {

    abstract fun add(component: Component)

    abstract fun remove(component: Component)

    abstract fun show(depth: Int): String
}

2. 建立 Composite 樹支

/**
 * Composite：樹支，擁有樹葉
 */
class Composite(name: String) : Component(name) {

    private val child: ArrayList<Component> = ArrayList()

    override fun add(component: Component) {
        child.add(component)
    }

    override fun remove(component: Component) {
        child.remove(component)
    }

    override fun show(depth: Int): String {
        val text = StringBuilder()

        for (i in 0 until depth) {
            text.append("-")
        }

        text.append("Composite name:$name")

        for (component in child) {
            val show = component.show(depth + 1)
            text.append("\n")
            text.append(show)
        }

        return text.toString()
    }
}

3. 建立 Leaf 樹葉

/**
 * Leaf：樹葉，結構最末端
 */
class Leaf(name: String) : Component(name) {

    override fun add(component: Component) {
        Log.d("TAG", "樹葉不可新增")
    }

    override fun remove(component: Component) {
        Log.d("TAG", "樹葉不可移除")
    }

    override fun show(depth: Int): String {
        val text = StringBuilder()
        for (i in 0 until depth) {
            text.append("-")
        }

        text.append("Leaf name:$name")

        return text.toString()
    }
}

合成模式測試

1. 測試程式碼

@Test
fun show() {
    val member = Composite("會員系統");
    val name = Composite("姓名")
    val age = Composite("年齡")
    val level = Composite("等級")
    member.add(name)
    member.add(age)
    member.add(level)
    name.add(Leaf("Andy"))
    name.add(Leaf("Leigh"))
    age.add(Leaf("30"))
    age.add(Leaf("25"))
    level.add(Leaf("Gold"))
    level.add(Leaf("Silver"))
    
    assertEquals("合成模式測試", member.show(0))
}

2. 輸出結果

Composite name:會員系統
-Composite name:姓名
--Leaf name:Andy
--Leaf name:Leigh
-Composite name:年齡
--Leaf name:30
--Leaf name:25
-Composite name:等級
--Leaf name:Gold
--Leaf name:Silver