[Go] Updated the 'callback' and 'extend' examples to match the 'director' one.

After the documentation update on how to utilize the director feature with
commit @17b1c1c the 'callback' and 'extend' examples needed an update as well.

Examples/go/callback/Makefile

@@ -1,6 +1,7 @@
 TOP        = ../..
 SWIG       = $(TOP)/../preinst-swig
 CXXSRCS    = callback.cxx
+GOSRCS     = gocallback.go
 TARGET     = example
 INTERFACE  = example.i
 SWIGOPT    =
@@ -9,8 +10,15 @@ check: build
 	$(MAKE) -f $(TOP)/Makefile SRCDIR='$(SRCDIR)' CXXSRCS='$(CXXSRCS)' TARGET='$(TARGET)' INTERFACE='$(INTERFACE)' go_run
 
 build:
-	$(MAKE) -f $(TOP)/Makefile SRCDIR='$(SRCDIR)' CXXSRCS='$(CXXSRCS)' SWIG='$(SWIG)' \
-	SWIGOPT='$(SWIGOPT)' TARGET='$(TARGET)' INTERFACE='$(INTERFACE)' go_cpp
+	if [ -n '$(SRCDIR)' ]; then \
+		cp $(GOSRCS:%=$(SRCDIR)/%) .; \
+	fi
+	@# Note: example.go gets generated by SWIG
+	$(MAKE) -f $(TOP)/Makefile SRCDIR='$(SRCDIR)' CXXSRCS='$(CXXSRCS)' GOSRCS='example.go $(GOSRCS)' \
+	SWIG='$(SWIG)' SWIGOPT='$(SWIGOPT)' TARGET='$(TARGET)' INTERFACE='$(INTERFACE)' go_cpp
 
 clean:
+	if [ -n '$(SRCDIR)' ]; then \
+		rm $(GOSRCS) || true; \
+	fi
 	$(MAKE) -f $(TOP)/Makefile SRCDIR='$(SRCDIR)' INTERFACE='$(INTERFACE)' go_clean

Examples/go/callback/example.h

@@ -20,4 +20,3 @@ public:
 	void setCallback(Callback *cb) { delCallback(); _callback = cb; }
 	void call() { if (_callback) _callback->run(); }
 };
-

Examples/go/callback/gocallback.go

@@ -0,0 +1,41 @@
+package example
+
+import (
+	"fmt"
+)
+
+type GoCallback interface {
+	Callback
+	deleteCallback()
+	IsGoCallback()
+}
+
+type goCallback struct {
+	Callback
+}
+
+func (p *goCallback) deleteCallback() {
+	DeleteDirectorCallback(p.Callback)
+}
+
+func (p *goCallback) IsGoCallback() {}
+
+type overwrittenMethodsOnCallback struct {
+	p Callback
+}
+
+func NewGoCallback() GoCallback {
+	om := &overwrittenMethodsOnCallback{}
+	p := NewDirectorCallback(om)
+	om.p = p
+
+	return &goCallback{Callback: p}
+}
+
+func DeleteGoCallback(p GoCallback) {
+	p.deleteCallback()
+}
+
+func (p *goCallback) Run() {
+	fmt.Println("GoCallback.Run")
+}

Examples/go/callback/index.html

@@ -12,67 +12,17 @@
 <H2>Implementing C++ callbacks in Go</H2>
 
 <p>
-This example illustrates how to use directors to implement C++
-callbacks in Go.
-</p>
-
-<p>
-Because Go and C++ use inheritance differently, you must call a
-different function to create a class which uses callbacks.  Instead of
-calling the usual constructor function whose name is <tt>New</tt>
-followed by the capitalized name of the class, you call a function
-named <tt>NewDirector</tt> followed by the capitalized name of the
-class.
-</p>
-
-<p>
-The first argument to the <tt>NewDirector</tt> function is an instance
-of a type.  The <tt>NewDirector</tt> function will return an interface
-value as usual.  However, when calling any method on the returned
-value, the program will first check whether the value passed
-to <tt>NewDirector</tt> implements that method.  If it does, the
-method will be called in Go.  This is true whether the method is
-called from Go code or C++ code.
-</p>
-
-<p>
-Note that the Go code will be called with just the Go value, not the
-C++ value.  If the Go code needs to call a C++ method on itself, you
-need to get a copy of the C++ object.  This is typically done as
-follows:
-
-<blockquote>
-<pre>
-type Child struct { abi Parent }
-func (p *Child) ChildMethod() {
-	p.abi.ParentMethod()
-}
-func f() {
-	p := &Child{nil}
-	d := NewDirectorParent(p)
-	p.abi = d
-	...
-}
-</pre>
-</blockquote>
-
-In other words, we first create the Go value.  We pass that to
-the <tt>NewDirector</tt> function to create the C++ value; this C++
-value will be created with an association to the Go value.  We then
-store the C++ value in the Go value, giving us the reverse
-association.  That permits us to call parent methods from the child.
-
-</p>
-
-<p>
-To delete a director object, use the function <tt>DeleteDirector</tt>
-followed by the capitalized name of the class.
+This example illustrates how to use directors to implement C++ callbacks in Go.
+See the <a href="../../../Doc/Manual/Go.html#Go_director_classes">Go Director
+Classes</a> documentation subsection for an in-depth explanation how to use the
+director feature.
 </p>
 
 <p>
 <ul>
-<li><a href="example.h">example.h</a>.  Header file containing some enums.
-<li><a href="example.i">example.i</a>.  Interface file.
+<li><a href="example.h">example.h</a>.  Header with the definition of the Caller and Callback classes.
+<li><a href="example.i">example.i</a>.  SWIG interface file.
+<li><a href="gocallback.go">gocallback.go</a>.  Go source with the definition of the GoCallback class.
 <li><a href="runme.go">runme.go</a>. Sample Go program.
 </ul>
 

Examples/go/callback/runme.go

@@ -16,26 +16,18 @@ func main() {
 	caller.Call()
 	caller.DelCallback()
 
-	callback = NewDirectorCallback(new(GoCallback))
+	go_callback := NewGoCallback()
 
 	fmt.Println()
 	fmt.Println("Adding and calling a Go callback")
-	fmt.Println("------------------------------------")
+	fmt.Println("--------------------------------")
 
-	caller.SetCallback(callback)
+	caller.SetCallback(go_callback)
 	caller.Call()
 	caller.DelCallback()
 
-	// Test that a double delete does not occur as the object has
-	// already been deleted from the C++ layer.
-	DeleteDirectorCallback(callback)
+	DeleteGoCallback(go_callback)
 
 	fmt.Println()
 	fmt.Println("Go exit")
 }
-
-type GoCallback struct{}
-
-func (p *GoCallback) Run() {
-	fmt.Println("GoCallback.Run")
-}