day7: homework 修改第7题

day7/homework/h7.cpp

@@ -44,6 +44,7 @@ catch (int e)
 ********************************************************************/
 
 #include <iostream>
+#include <typeinfo>
 
 using namespace std;
 
@@ -74,52 +75,66 @@ public:
 int main()
 {
     Animal *ap = new Animal(); // 创建一个 Animal 类型的指针
+
     try
     {
         Cat *cp = dynamic_cast<Cat *>(ap); // 将其转换为 Cat 类型的指针
+        if (cp)
             cp->meow();
+        else
+            throw 1;
     }
-    catch (int e)
+    catch (int &e)
     {
-        cout << "dynamic_cast 将 Animal 转换为 Cat 失败" << endl
-             << e << endl;
+        cout << "dynamic_cast 将 Animal 转换为 Cat 失败" << endl;
     }
 
     Animal *ap2 = new Animal(); // 创建一个 Animal 类型的指针
     try
     {
         Dog *dp = dynamic_cast<Dog *>(ap2); // 将其转换为 Dog 类型的指针
+        if (dp)
             dp->bark();
+        else
+            throw 1;
     }
-    catch (int e)
+    catch (int &e)
     {
-        cout << "dynamic_cast 将 Animal 转换为 Dog 失败" << endl
-             << e << endl;
+        cout << "dynamic_cast 将 Animal 转换为 Dog 失败" << endl;
     }
 
     Cat *cp2 = new Cat(); // 创建一个 Cat 类型的指针
     try
     {
         Animal *ap3 = dynamic_cast<Animal *>(cp2); // 将其转换为 Animal 类型的指针
+        if (ap3)
             cout << "dynamic_cast 将 Cat 转换为 Animal 成功" << endl;
+        else
+            throw 1;
     }
-    catch (int e)
+    catch (int &e)
     {
-        cout << "dynamic_cast 将 Cat 转换为 Animal 失败" << endl
-             << e << endl;
+        cout << "dynamic_cast 将 Cat 转换为 Animal 失败" << endl;
     }
 
     Dog *dp2 = new Dog(); // 创建一个 Dog 类型的指针
     try
     {
         Animal *ap4 = dynamic_cast<Animal *>(dp2); // 将其转换为 Animal 类型的指针
+        if (ap4)
             cout << "dynamic_cast 将 Dog 转换为 Animal 成功" << endl;
+        else
+            throw 1;
     }
-    catch (int e)
+    catch (int &e)
     {
-        cout << "dynamic_cast 将 Dog 转换为 Animal 失败" << endl
-             << e << endl;
+        cout << "dynamic_cast 将 Dog 转换为 Animal 失败" << endl;
     }
 
+    delete ap;
+    delete ap2;
+    delete cp2;
+    delete dp2;
+
     return 0;
 }

day7/homework/h7_2.cpp

@@ -0,0 +1,105 @@
+#include <iostream>
+#include <typeinfo>
+
+class Animal
+{
+public:
+    virtual ~Animal() {}
+};
+
+class Cat : public Animal
+{
+public:
+    void meow()
+    {
+        std::cout << "Meow!" << std::endl;
+    }
+};
+
+class Dog : public Animal
+{
+public:
+    void bark()
+    {
+        std::cout << "Woof!" << std::endl;
+    }
+};
+
+int main()
+{
+    // 任务1：将Animal类型指针转换为Cat类型指针
+    Animal *animal1 = new Cat();
+    try
+    {
+        Cat *cat = dynamic_cast<Cat *>(animal1);
+        if (cat)
+        {
+            cat->meow();
+        }
+        else
+        {
+            throw 1;
+        }
+    }
+    catch (int e)
+    {
+        std::cout << "转换失败：无法将Animal类型转换为Cat类型。" << std::endl;
+    }
+
+    // 任务2：将Animal类型指针转换为Dog类型指针
+    Animal *animal2 = new Dog();
+    try
+    {
+        Dog *dog = dynamic_cast<Dog *>(animal2);
+        if (dog)
+        {
+            dog->bark();
+        }
+        else
+        {
+            throw 2;
+        }
+    }
+    catch (int e)
+    {
+        std::cout << "转换失败：无法将Animal类型转换为Dog类型。" << std::endl;
+    }
+
+    // 任务3：将Cat类型指针转换为Animal类型指针
+    Cat *cat2 = new Cat();
+    try
+    {
+        Animal *animal3 = dynamic_cast<Animal *>(cat2);
+        if (animal3)
+        {
+            std::cout << "转换成功：Cat类型成功转换为Animal类型。" << std::endl;
+        }
+    }
+    catch (const std::bad_cast &e)
+    {
+        std::cout << "转换失败：" << e.what() << std::endl;
+    }
+
+    // 任务4：将Dog类型指针转换为Animal类型指针
+    Dog *dog2 = new Dog();
+    try
+    {
+        Animal *animal4 = dynamic_cast<Animal *>(dog2);
+        if (animal4)
+        {
+            std::cout << "转换成功：Dog类型成功转换为Animal类型。" << std::endl;
+        }
+    }
+    catch (const std::bad_cast &e)
+    {
+        std::cout << "转换失败：" << e.what() << std::endl;
+    }
+
+    // 释放内存
+    delete animal1;
+    delete animal2;
+    delete cat2;
+    delete dog2;
+
+    return 0;
+}