Add faux-inheritance example

CMakeLists.txt

@@ -203,6 +203,8 @@ if(BUILD_SAMPLES)
   target_link_libraries(example ${LIBS})
   add_executable(memory_leak_test samples/memory_leak_test.cpp)
   target_link_libraries(memory_leak_test ${LIBS})
+  add_executable(inheritance samples/inheritance.cpp)
+  target_link_libraries(inheritance ${LIBS})
 endif()
 
 

samples/inheritance.cpp

@@ -0,0 +1,134 @@
+#include <chaiscript/chaiscript.hpp>
+#include <chaiscript/chaiscript_stdlib.hpp>
+
+class BaseClass
+{
+  public:
+    BaseClass()
+    {
+    }
+
+    virtual ~BaseClass() = default;
+
+    virtual std::string doSomething(float, double) const = 0;
+
+
+    void setValue(const std::string &t_val) {
+      if (validateValue(t_val))
+      {
+        m_value = t_val;
+      }
+    }
+
+    std::string getValue() const {
+      return m_value;
+    }
+
+  protected:
+    virtual bool validateValue(const std::string &t_val) = 0;
+
+  private:
+    std::string m_value;
+};
+
+class ChaiScriptDerived : public BaseClass
+{
+  public:
+    ChaiScriptDerived(const std::vector<chaiscript::Boxed_Value> &t_funcs)
+    {
+      // using the range-checked .at() methods to give us an exception
+      // instead of a crash if the user passed in too-few params
+      tie(t_funcs.at(0), m_doSomethingImpl);
+      tie(t_funcs.at(1), m_validateValueImpl);
+    }
+
+    std::string doSomething(float f, double d) const override
+    {
+      assert(m_doSomethingImpl);
+      return m_doSomethingImpl(*this, f, d);
+    }
+
+  protected:
+    bool validateValue(const std::string &t_val) override
+    {
+      assert(m_validateValueImpl);
+      return m_validateValueImpl(*this, t_val);
+    }
+
+  private:
+    template<typename Param>
+    void tie(const chaiscript::Boxed_Value &t_func, Param &t_param)
+    {
+      t_param = chaiscript::boxed_cast<Param>(t_func);
+    }
+
+    std::function<std::string (const ChaiScriptDerived&, float, double)> m_doSomethingImpl;
+    std::function<bool (ChaiScriptDerived&, const std::string &t_val)> m_validateValueImpl;
+};
+
+int main()
+{
+  chaiscript::ChaiScript chai(chaiscript::Std_Lib::library());
+  chai.add(chaiscript::fun(&BaseClass::doSomething), "doSomething");
+  chai.add(chaiscript::fun(&BaseClass::setValue), "setValue");
+  chai.add(chaiscript::fun(&BaseClass::getValue), "getValue");
+  chai.add(chaiscript::constructor<ChaiScriptDerived (const std::vector<chaiscript::Boxed_Value> &)>(), "ChaiScriptDerived");
+  chai.add(chaiscript::base_class<BaseClass, ChaiScriptDerived>());
+  chai.add(chaiscript::user_type<BaseClass>(), "BaseClass");
+  chai.add(chaiscript::user_type<ChaiScriptDerived>(), "ChaiScriptDerived");
+
+  std::string script = R""(
+    def MakeDerived() {
+      return ChaiScriptDerived(
+          // create a dynamically created array and pass it in to the constructor
+          [
+          fun(this, f, d) {
+            // see here that we are calling back into the 'this' pointer
+            return "${this.getValue()}${f * d}";
+          },
+
+          fun(this, new_val) {
+            if (new_val.size() < 5) {
+              true;
+            } else {
+              print("String ${new_val} is too long");
+              false;
+            }
+          }
+          ]
+          );
+    }
+
+    var myderived := MakeDerived(); // avoid a copy by using reference assignment :=
+
+    )"";
+
+  chai.eval(script);
+  
+  BaseClass &myderived = chai.eval<ChaiScriptDerived&>("myderived");
+
+  // at this point in the code myderived is both a ChaiScript variable and a C++ variable. In both cases
+  // it is a derivation of BaseClass, and the implementation is provided via ChaiScript functors
+  // assigned in the MakeDerived() factory function
+  //
+  // Notice that our validateValue() function has a requirement that the new string be < 5 characters long
+
+  myderived.setValue("1234");
+  assert(myderived.getValue() == "1234");
+
+  // chaiscript defined function will print out an error message and refuse to allow the setting
+  myderived.setValue("12345");
+  assert(myderived.getValue() == "1234");
+
+
+  chai.eval("myderived.setValue(\"new\")"); // set the value via chaiscript
+  assert(myderived.getValue() == "new");
+
+  // call the other derived method via chaiscript and return the value to c++ land:
+  std::string retval = chai.eval<std::string>("myderived.doSomething(2,4.3)");
+  assert(retval == "new8.6");
+
+  // The whole process is fully orthogonal
+}
+
+