add LambdaBase

iface/lambda.hh

@@ -6,6 +6,8 @@
 #include <vector>
 
 #include "iface/common/dealer.hh"
+#include "iface/common/exception.hh"
+#include "iface/common/observer.hh"
 #include "iface/common/value.hh"
 
 namespace nf7 {
@@ -13,10 +15,9 @@ namespace nf7 {
 class Lambda {
  public:
   Lambda() = delete;
-  Lambda(std::shared_ptr<Taker<Value>>&& taker,
-         std::shared_ptr<Maker<Value>>&& maker) noexcept
-      : taker_(std::move(taker)), maker_(maker) {
-  }
+  Lambda(const std::shared_ptr<Taker<Value>>& taker,
+         const std::shared_ptr<Maker<Value>>& maker) noexcept
+      : taker_(std::move(taker)), maker_(maker) { }
   virtual ~Lambda() = default;
 
   Lambda(const Lambda&) = delete;
@@ -32,4 +33,31 @@ class Lambda {
   const std::shared_ptr<Maker<Value>> maker_;
 };
 
+class LambdaBase : public Lambda, private Observer<Value> {
+ public:
+  LambdaBase(DealerMeta&& takerMeta = {}, DealerMeta&& makerMeta = {})
+  try : LambdaBase(std::make_shared<Taker<Value>>(std::move(takerMeta)),
+                   std::make_shared<Emitter<Value>>(std::move(makerMeta))) {
+  } catch (const std::bad_alloc&) {
+    throw Exception {"memory shortage"};
+  }
+
+ private:
+  LambdaBase(const std::shared_ptr<Taker<Value>>&   taker,
+             const std::shared_ptr<Emitter<Value>>& maker)
+      : Lambda(taker, maker), Observer<Value>(*taker), emitter_(maker) { }
+
+ protected:
+  virtual void Main(const Value&) noexcept = 0;
+
+  const std::shared_ptr<Emitter<Value>>& emitter() const noexcept {
+    return emitter_;
+  }
+
+ private:
+  void Notify(const Value& v) noexcept override { Main(v); }
+
+  const std::shared_ptr<Emitter<Value>> emitter_;
+};
+
 }  // namespace nf7