add a few new patterns

Author: xiao cheng

.vscode/launch.json

@@ -8,7 +8,7 @@
             "name": "(lldb) Launch",
             "type": "cppdbg",
             "request": "launch",
-            "program": "${workspaceFolder}/bin/cpp11_threadsafe_queue",
+            "program": "${workspaceFolder}/bin/Interpreter",
             "args": [],
             "stopAtEntry": false,
             "cwd": "${workspaceFolder}",

CMakeLists.txt

@@ -25,4 +25,10 @@ if(Boost_FOUND)
     add_subdirectory(Composite)
     add_subdirectory(Delegation)
     add_subdirectory(Facade)
+    add_subdirectory(Flyweight)
+    add_subdirectory(Proxy)
+    add_subdirectory(ChainOfRes)
+    add_subdirectory(CommandPattern)
+    add_subdirectory(Interpreter)
+    add_subdirectory(IteratorPattern)
 endif()

ChainOfRes/CMakeLists.txt

@@ -0,0 +1,18 @@
+cmake_minimum_required(VERSION 3.8)
+
+project(COR1)
+
+include_directories(${Boost_INCLUDE_DIRS})
+
+add_executable(${PROJECT_NAME} main.cpp)
+
+target_link_libraries(${PROJECT_NAME} PUBLIC 
+ gtest_main
+ ${Boost_LIBRARIES}
+ )
+
+ add_test(
+     NAME ${PROJECT_NAME}
+     COMMAND ${PROJECT_NAME}
+ )
+ install(TARGETS ${PROJECT_NAME} RUNTIME DESTINATION ../bin)

ChainOfRes/main.cpp

@@ -0,0 +1,92 @@
+#include <iostream>
+#include <vector>
+#include <ctime>
+using namespace std;
+
+class Base
+{
+    Base *next; // 1. "next" pointer in the base class
+  public:
+    Base()
+    {
+        next = 0;
+    }
+    void setNext(Base *n)
+    {
+        next = n;
+    }
+    void add(Base *n)
+    {
+        if (next)
+            next->add(n);
+        else
+            next = n;
+    }
+    // 2. The "chain" method in the base class always delegates to the next obj
+    virtual void handle(int i)
+    {
+        next->handle(i);
+    }
+};
+
+class Handler1 : public Base
+{
+  public:
+    /*virtual*/ void handle(int i)
+    {
+        if (rand() % 3)
+        {
+            // 3. Don't handle requests 3 times out of 4
+            cout << "H1 passed " << i << "  ";
+            Base::handle(i); // 3. Delegate to the base class
+        }
+        else
+            cout << "H1 handled " << i << "  ";
+    }
+};
+
+class Handler2 : public Base
+{
+  public:
+    /*virtual*/ void handle(int i)
+    {
+        if (rand() % 3)
+        {
+            cout << "H2 passed " << i << "  ";
+            Base::handle(i);
+        }
+        else
+            cout << "H2 handled " << i << "  ";
+    }
+};
+
+class Handler3 : public Base
+{
+  public:
+    /*virtual*/ void handle(int i)
+    {
+        if (rand() % 3)
+        {
+            cout << "H3 passed " << i << "  ";
+            Base::handle(i);
+        }
+        else
+            cout << "H3 handled " << i << "  ";
+    }
+};
+
+int main()
+{
+    srand(time(0));
+    Handler1 root;
+    Handler2 two;
+    Handler3 thr;
+    root.add(&two);
+    root.add(&thr);
+    thr.setNext(&root);
+    for (int i = 1; i < 10; i++)
+    {
+        root.handle(i);
+        cout << '\n';
+    }
+}

CommandPattern/CMakeLists.txt

@@ -0,0 +1,15 @@
+cmake_minimum_required(VERSION 3.8)
+
+project(CommandPattern)
+
+include_directories(${Boost_INCLUDE_DIRS})
+
+add_executable(simple_commands simple_commands.cpp)
+add_executable(macro_commands macro_commands.cpp)
+
+target_link_libraries(simple_commands PUBLIC gtest_main ${Boost_LIBRARIES})
+target_link_libraries(macro_commands PUBLIC gtest_main ${Boost_LIBRARIES})
+
+install(TARGETS simple_commands macro_commands RUNTIME DESTINATION ../bin)
+
+

CommandPattern/bank_command.cpp

@@ -0,0 +1,128 @@
+#include <iostream>
+#include <string>
+#include <vector>
+using namespace std;
+
+struct BankAccount
+{
+    int balance = 0;
+    int overdraft_limit = -500;
+
+    void deposit(int amount)
+    {
+        balance += amount;
+        cout << "deposited " << amount << ", balance now " << balance << "\n";
+    }
+
+    void withdraw(int amount)
+    {
+        if (balance - amount >= overdraft_limit)
+        {
+            balance -= amount;
+            cout << "withdrew " << amount << ", balance now " << balance << "\n";
+        }
+    }
+};
+
+struct Command
+{
+    virtual ~Command() = default;
+    virtual void call() const = 0;
+    virtual void undo() const = 0;
+};
+
+// should really be BankAccountCommand
+struct BankAccountCommand : Command
+{
+    BankAccount &account;
+    enum Action
+    {
+        deposit,
+        withdraw
+    } action;
+    int amount;
+
+    BankAccountCommand(BankAccount &account,
+                       const Action action, const int amount)
+        : account(account), action(action), amount(amount) {}
+
+    void call() const override
+    {
+        switch (action)
+        {
+        case deposit:
+            account.deposit(amount);
+            break;
+        case withdraw:
+            account.withdraw(amount);
+            break;
+        default:
+            break;
+        }
+    }
+
+    void undo() const override
+    {
+        switch (action)
+        {
+        case withdraw:
+            account.deposit(amount);
+            break;
+        case deposit:
+            account.withdraw(amount);
+            break;
+        default:
+            break;
+        }
+    }
+};
+
+// vector doesn't have virtual dtor, but who cares?
+struct CompositeBankAccountCommand
+    : vector<BankAccountCommand>,
+      Command
+{
+    CompositeBankAccountCommand(const initializer_list<value_type> &items)
+        : vector<BankAccountCommand>(items) {}
+
+    void call() const override
+    {
+        for (auto &cmd : *this)
+            cmd.call();
+    }
+
+    void undo() const override
+    {
+        for (auto &cmd : *this)
+            cmd.undo();
+    }
+};
+
+int main()
+{
+    BankAccount ba;
+    /*vector<BankAccountCommand> commands{*/
+    CompositeBankAccountCommand commands{
+        BankAccountCommand{ba, BankAccountCommand::deposit, 100},
+        BankAccountCommand{ba, BankAccountCommand::withdraw, 200}};
+
+    cout << ba.balance << endl;
+
+    // apply all the commands
+    /*for (auto& cmd : commands)
+  {
+    cmd.call();
+  }*/
+    commands.call();
+
+    cout << ba.balance << endl;
+
+    /*for_each(commands.rbegin(), commands.rend(),
+    [](const BankAccountCommand& cmd) { cmd.undo(); });*/
+    commands.undo();
+
+    cout << ba.balance << endl;
+
+    getchar();
+    return 0;
+}

CommandPattern/command_test.cpp

@@ -0,0 +1,77 @@
+#include <iostream>
+#include <vector>
+using namespace std;
+
+struct Command
+{
+    enum Action
+    {
+        deposit,
+        withdraw
+    } action;
+    int amount{0};
+    bool success{false};
+};
+
+struct Account
+{
+    int balance{0};
+
+    void process(Command &cmd)
+    {
+        switch (cmd.action)
+        {
+        case Command::deposit:
+            balance += cmd.amount;
+            cmd.success = true;
+            break;
+        case Command::withdraw:
+            cmd.success = (balance >= cmd.amount);
+            if (cmd.success)
+                balance -= cmd.amount;
+            break;
+        }
+    }
+};
+
+#include "gtest/gtest.h"
+
+//#include "helpers/iohelper.h"
+
+//#include "exercise.cpp"
+
+namespace
+{
+class Evaluate : public testing::Test
+{
+  public:
+};
+
+TEST_F(Evaluate, LotsOfAccountTests)
+{
+    Account a;
+    Command command{Command::deposit, 100};
+    a.process(command);
+
+    ASSERT_EQ(100, a.balance);
+    ASSERT_TRUE(command.success);
+
+    command = Command{Command::withdraw, 50};
+    a.process(command);
+
+    ASSERT_EQ(50, a.balance);
+    ASSERT_TRUE(command.success);
+
+    command = Command{Command::withdraw, 150};
+    a.process(command);
+
+    ASSERT_EQ(50, a.balance);
+    ASSERT_FALSE(command.success);
+}
+} // namespace
+
+int main(int ac, char *av[])
+{
+    testing::InitGoogleTest(&ac, av);
+    return RUN_ALL_TESTS();
+}