Proxy Pattern

_21proxy/Printable.kt

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+package _21proxy
+
+interface Printable {
+    var name: String?
+    fun print(string: String)
+}

_21proxy/Printer.kt

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+package _21proxy
+
+class Printer(override var name: String?) : Printable {
+    init {
+        heavyJob("Printer 인스턴스 생성 중 name = $name")
+    }
+
+    override fun print(string: String) {
+        println("===$name===")
+        println(string)
+    }
+
+    private fun heavyJob(message: String) {
+        println(message)
+        repeat(5) {
+            Thread.sleep(1000)
+            println(".")
+        }
+    }
+}

_21proxy/PrinterProxy.kt

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+package _21proxy
+
+class PrinterProxy(initialName: String?) : Printable {
+    private var real: Printer? = null
+
+    override var name: String? = initialName
+        @Synchronized
+        set(value) {
+            field = value
+            if (real != null) {
+                real?.name = value
+            }
+        }
+
+    override fun print(string: String) {
+        realize()
+        real?.print(string)
+    }
+
+    @Synchronized
+    private fun realize() {
+        if (real == null) {
+            real = Printer(name)
+        }
+    }
+}

_21proxy/main.kt

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+package _21proxy
+
+fun main() {
+    val p = PrinterProxy("Alice")
+    println("이름은 현재 ${p.name} 입니다.")
+    p.name = "Bob"
+    println("이름은 현재 ${p.name} 입니다.")
+    p.print("Hello World!")
+}