Add BoolSwitchFlag class to model boolean input parameters

src/anbox/cli.cpp

@@ -44,9 +44,10 @@ static constexpr const char* option = "    --%1% %2%";
 void add_to_desc_for_flags(po::options_description& desc,
                            const std::set<cli::Flag::Ptr>& flags) {
   for (auto flag : flags) {
-    auto v = po::value<std::string>()->notifier(
-        [flag](const std::string& s) { flag->notify(s); });
-    desc.add_options()(flag->name().as_string().c_str(), v,
+    po::value_semantic *spec = nullptr;
+    flag->specify_option(spec);
+    if (!spec) continue;
+    desc.add_options()(flag->name().as_string().c_str(), spec,
                        flag->description().as_string().c_str());
   }
 }

src/anbox/cli.h

-/*
+/*
  * Copyright (C) 2016 Canonical, Ltd.
  *
  * This program is free software; you can redistribute it and/or modify
@@ -31,6 +31,8 @@
 #include "anbox/do_not_copy_or_move.h"
 #include "anbox/optional.h"
 
+#include <boost/program_options.hpp>
+
 namespace anbox {
 namespace cli {
 
@@ -76,16 +78,19 @@ typedef SizeConstrainedString<80> Description;
 /// @brief Flag models an input parameter to a command.
 class Flag : public DoNotCopyOrMove {
  public:
+  typedef boost::program_options::value_semantic* Specification;
+
   // Safe us some typing.
   typedef std::shared_ptr<Flag> Ptr;
 
-  /// @brief notify announces a new value to the flag.
-  virtual void notify(const std::string& value) = 0;
   /// @brief name returns the name of the Flag.
   const Name& name() const;
   /// @brief description returns a human-readable description of the flag.
   const Description& description() const;
 
+  /// @brief specify the program option of the flag.
+  virtual void specify_option(Specification& spec) = 0;
+
  protected:
   /// @brief Flag creates a new instance, initializing name and description
   /// from the given values.
@@ -115,12 +120,15 @@ class TypedFlag : public Flag {
   /// @brief value returns the optional value associated with the flag.
   const Optional<T>& value() const { return value_; }
 
-  /// @brief notify tries to unwrap a value of type T from value.
-  void notify(const std::string& s) override {
-    std::stringstream ss{s};
-    T value;
-    ss >> value;
-    value_ = value;
+  /// @brief Option generated by specify_option tries to unwrap a value
+  /// of type T from value.
+  void specify_option(Flag::Specification& spec) override {
+    spec = boost::program_options::value<std::string>()->notifier([&](const std::string& s) {
+      std::stringstream ss{s};
+      T value;
+      ss >> value;
+      value_ = value;
+    });
   }
 
  private:
@@ -141,11 +149,15 @@ class TypedReferenceFlag : public Flag {
   TypedReferenceFlag(const Name& name, const Description& description, T& value)
       : Flag{name, description}, value_{value} {}
 
-  /// @brief notify tries to unwrap a value of type T from value,
-  /// relying on operator>> to read from given string s.
-  void notify(const std::string& s) override {
-    std::stringstream ss{s};
-    ss >> value_.get();
+  /// @brief Option generated by specify_option tries to unwrap a value of type T
+  /// from value, relying on operator>> to read from given string s.
+  void specify_option(Flag::Specification& spec) override {
+    spec = boost::program_options::value<std::string>()->notifier([&](const std::string& s) {
+      std::stringstream ss{s};
+      T value;
+      ss >> value;
+      value_ = value;
+    });
   }
 
  private:
@@ -153,9 +165,8 @@ class TypedReferenceFlag : public Flag {
 };
 
 /// @brief OptionalTypedReferenceFlag handles Optional<T> references, making
-/// sure that
-/// a value is always read on notify, even if the Optional<T> wasn't initialized
-/// previously.
+/// sure that a value is always read on notify, even if the Optional<T> wasn't
+/// initialized previously.
 template <typename T>
 class OptionalTypedReferenceFlag : public Flag {
  public:
@@ -165,18 +176,40 @@ class OptionalTypedReferenceFlag : public Flag {
                              Optional<T>& value)
       : Flag{name, description}, value_{value} {}
 
-  /// @brief notify tries to unwrap a value of type T from value.
-  void notify(const std::string& s) override {
-    std::stringstream ss{s};
-    T value;
-    ss >> value;
-    value_.get() = value;
+  /// @brief Option generated by specify_option tries to unwrap a value of
+  /// type T from value.
+  void specify_option(Flag::Specification& spec) override {
+    spec = boost::program_options::value<std::string>()->notifier([&](const std::string& s) {
+      std::stringstream ss{s};
+      T value;
+      ss >> value;
+      value_.get() = value;
+    });
   }
 
  private:
   std::reference_wrapper<Optional<T>> value_;
 };
 
+/// @brief BoolSwitchFlag implements Flag, updating the given mutable reference
+/// to a boolean value.
+class BoolSwitchFlag : public Flag {
+ public:
+  typedef std::shared_ptr<BoolSwitchFlag> Ptr;
+
+  BoolSwitchFlag(const Name& name, const Description& description, bool& value)
+    : Flag{name, description}, value_(value) {}
+
+  /// @brief Option generated by specify_option tries to unwrap a boolean
+  /// value from value.
+  void specify_option(Flag::Specification& spec) override {
+    spec = boost::program_options::bool_switch(&value_.get());
+  }
+
+ private:
+  std::reference_wrapper<bool> value_;
+};
+
 /// @brief Command abstracts an individual command available from the daemon.
 class Command : public DoNotCopyOrMove {
  public:
@@ -337,6 +370,14 @@ typename OptionalTypedReferenceFlag<T>::Ptr make_flag(const Name& name,
   return std::make_shared<OptionalTypedReferenceFlag<T>>(name, desc, value);
 }
 
+/// @brief make_flag returns a flag with the given name and description,
+/// updating the given boolean value.
+inline BoolSwitchFlag::Ptr make_flag(const Name& name,
+                                     const Description &desc,
+                                     bool &value) {
+  return std::make_shared<BoolSwitchFlag>(name, desc, value);
+}
+
 }  // namespace cli
 }  // namespace anbox