Extension As Member.

app/src/main/java/com/boycoder/kotlinjetpackinaction/chapter/c06/TestExtAsMember.kt

@@ -0,0 +1,55 @@
+package com.boycoder.kotlinjetpackinaction.chapter.c06
+
+/**
+ * Created by zhu.tao on 2020/7/31.
+ */
+
+open class Base { }
+
+class Derived : Base() { }
+
+open class BaseCaller {
+    open fun Base.printFunctionInfo() {
+        println("Base extension function in BaseCaller")
+    }
+
+    open fun Derived.printFunctionInfo() {
+        println("Derived extension function in BaseCaller")
+    }
+
+    val Derived.test: Int
+        get() = 1
+
+    fun call(b: Base) {
+        b.printFunctionInfo()   // 调用扩展函数
+    }
+}
+
+class DerivedCaller: BaseCaller() {
+    override fun Base.printFunctionInfo() {
+        println("Base extension function in DerivedCaller")
+    }
+
+    override fun Derived.printFunctionInfo() {
+        println("Derived extension function in DerivedCaller")
+    }
+}
+
+/**
+ * 步骤：先运行代码，然后调试代码，最后反编译代码。
+ *
+ * 理解这个例子的关键在于：
+ *
+ * BaseCaller().call(), DerivedCaller().call() 是多态的。
+ *
+ * 而 call 函数里的 base.printFunctionInfo() 是静态的。
+ *
+ * 这段话一定要结合反编译后的代码看
+ *
+ */
+fun main() {
+    BaseCaller().call(Base())
+    BaseCaller().call(Derived())
+    DerivedCaller().call(Base())
+    DerivedCaller().call(Derived())
+}