use the attributeID to activate the right closure

...under the assumption that the number of attributes is small,
using just a chained sequence of inlined if-statements
"would be acceptable"

src/lib/diff/tree-mutator.hpp

@@ -77,7 +77,6 @@ namespace diff{
     template<class PAR>
     class Builder;
     
-    ////////TODO only preliminary....
     typedef Literal ID;
     using Attribute = DataCap;
   }
@@ -124,11 +123,7 @@ namespace diff{
           UNIMPLEMENTED("expose a recursive TreeMutator to transform the denoted child");
         }
       
-      virtual void
+      virtual void setAttribute (ID, Attribute&) { /* do nothing by default */ }
-      setAttribute (ID id, Attribute& newValue)
-        {
-          std::cout << "Empty Base Impl: apply a value change to the named attribute"<<std::endl;      ////////////////TODO empty implementation should be NOP
-        }
       
       /**
        * start building a custom adapted tree mutator,
@@ -144,19 +139,22 @@ namespace diff{
     struct ChangeOperation
       : PAR
       {
+        ID attribID_;
         function<void(string)> change_;
         
         virtual void
         setAttribute (ID id, Attribute& newValue)
           {
-            // Decorator-style chained invocation of inherited implementation
+            if (id == attribID_)
-            PAR::setAttribute(id, newValue);
+              change_(newValue.get<string>());
             
-            change_(newValue.get<string>());
+            else // delegate to other closures (Decorator-style)
+              PAR::setAttribute(id, newValue);
           }
         
-        ChangeOperation(function<void(string)> clo, PAR const& chain)
+        ChangeOperation(ID id, function<void(string)> clo, PAR const& chain)
           : PAR(chain)
+          , attribID_(id)
           , change_(clo)
           { }
       };
@@ -177,7 +175,7 @@ namespace diff{
         Builder<Change>
         change (Literal attributeID, function<void(string)> closure)
           {
-            return Change (closure, *this);
+            return Change (attributeID, closure, *this);
           }
       };
 

tests/15library.tests

@@ -222,7 +222,10 @@ return: 0
 END
 
 
-PLANNED "GenericTreeMutator_test" GenericTreeMutator_test <<END
+TEST "Generic recursive mutation with closure binding" GenericTreeMutator_test <<END
+out: concrete TreeMutator .+Builder<.+ChangeOperation<.+TreeMutator
+out-lit: "data" closure received something that would be acceptable
+out-lit: localData changed to: that would be acceptable
 return: 0
 END
 

tests/library/diff/generic-tree-mutator-test.cpp

@@ -92,24 +92,24 @@ namespace test{
           string localData;
           auto mutator =
           TreeMutator::build()
-            .change("something", [&](string val)
+            .change("data", [&](string val)
               {
-                cout << "Oink-Oink"<<endl;
+                cout << "\"data\" closure received something "<<val<<endl;
-                localData = "Oink-Oink";
-              })
-            .change("something", [&](string val)
-              {
-                cout << "Change closure invoked with val="<<val<<endl;
                 localData = val;
               });
           
-          cout << "concrete TreeMutator type="<< demangleCxx (showType (mutator)) <<endl;
+          cout << "concrete TreeMutator size=" << sizeof(mutator)
+               << " type="<< demangleCxx (showType (mutator))
+               << endl;
           
           CHECK (isnil (localData));
-              Attribute testAttribute(string ("boing"));
+          Attribute testAttribute(string ("that would be acceptable"));
-              mutator.setAttribute ("zoing", testAttribute);
+          mutator.setAttribute ("lore", testAttribute);
+          CHECK ( isnil (localData)); // nothing happens, nothing changed
+          mutator.setAttribute ("data", testAttribute);
           CHECK (!isnil (localData));
-          cout << "localData changed to:"<<localData<<endl;
+          cout << "localData changed to: "<<localData<<endl;
+          CHECK (localData == "that would be acceptable");
         }