Merge pull request #13 from DoctorLai/oop-with-exception

Add OOP with exception

Author: doctorlai-msrc

README.md

@@ -32,6 +32,7 @@ Examples include (and will expand to):
         * [rot47](./rot47/)
 * OOP
     * [virtual-interface](./virtual-interface/)
+    * [oop-with-exception](./oop-with-exception/)
 
 ---
 

oop-with-exception/Makefile

@@ -0,0 +1,31 @@
+# pull in shared compiler settings
+include ../common.mk
+
+# per-example flags
+# CXXFLAGS += -pthread
+
+## get it from the folder name
+TARGET := $(notdir $(CURDIR))
+## all *.cpp files in this folder
+SRCS   := $(wildcard *.cpp)
+OBJS   := $(SRCS:.cpp=.o)
+
+all: $(TARGET)
+
+$(TARGET): $(OBJS)
+	$(CXX) $(CXXFLAGS) -o $@ $^
+
+%.o: %.cpp
+	$(CXX) $(CXXFLAGS) -c $< -o $@
+
+run: $(TARGET)
+	./$(TARGET) $(ARGS)
+
+clean:
+	rm -f $(OBJS) $(TARGET)
+
+# Delegates to top-level Makefile
+check-format:
+	$(MAKE) -f ../Makefile check-format DIR=$(CURDIR)
+
+.PHONY: all clean run check-format

oop-with-exception/main.cpp

@@ -0,0 +1,47 @@
+/**
+This example creates two classes A and B, where class B is a member of class A.
+And in the constructor of class A, it prints a message and throws an exception.
+So what would be the output?
+
+B's constructor called.
+A's constructor called.
+B's destructor called.
+Caught exception: Exception in A's constructor
+
+If an exception leaves a constructor, the object’s destructor does not run, because the object never finished
+construction. But destructors for already-constructed members/base-subobjects do run.
+*/
+
+#include <iostream>
+#include <stdexcept>
+
+class B
+{
+  public:
+    B() { std::cout << "B's constructor called." << std::endl; }
+    ~B() { std::cout << "B's destructor called." << std::endl; }
+};
+
+class A
+{
+  private:
+    B b; // Member of class B
+  public:
+    A()
+    {
+        std::cout << "A's constructor called." << std::endl;
+        throw std::runtime_error("Exception in A's constructor");
+    }
+    ~A() { std::cout << "A's destructor called." << std::endl; }
+};
+
+int
+main()
+{
+    try {
+        A a; // Attempt to create an instance of A
+    } catch (const std::exception& e) {
+        std::cout << "Caught exception: " << e.what() << std::endl;
+    }
+    return 0;
+}

oop-with-exception/oop-with-exception

@@ -0,0 +1,5 @@
+#!/bin/bash
+
+set -ex
+
+./oop-with-exception