new tasks

Task/Delegates/C/delegates.c

@@ -0,0 +1,86 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+typedef const char * (*Responder)( int p1);
+
+typedef struct sDelegate {
+    Responder operation;
+} *Delegate;
+
+/* Delegate class constructor */
+Delegate NewDelegate( Responder rspndr )
+{
+    Delegate dl = malloc(sizeof(struct sDelegate));
+    dl->operation = rspndr;
+    return dl;
+}
+
+/* Thing method of Delegate */
+const char *DelegateThing(Delegate dl, int p1)
+{
+    return  (dl->operation)? (*dl->operation)(p1) : NULL;
+}
+
+/** * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+typedef struct sDelegator {
+    int     param;
+    char    *phrase;
+    Delegate delegate;
+} *Delegator;
+
+const char * defaultResponse( int p1)
+{
+    return "default implementation";
+}
+
+static struct sDelegate defaultDel = { &defaultResponse };
+
+/* Delegator class constructor */
+Delegator NewDelegator( int p, char *phrase)
+{
+    Delegator d  = malloc(sizeof(struct sDelegator));
+    d->param = p;
+    d->phrase = phrase;
+    d->delegate = &defaultDel;	/* default delegate */
+    return d;
+}
+
+/* Operation method of Delegator */
+const char *Delegator_Operation( Delegator theDelegator, int p1, Delegate delroy)
+{
+    const char *rtn;
+    if (delroy) {
+        rtn = DelegateThing(delroy, p1);
+        if (!rtn) {			/* delegate didn't handle 'thing' */
+            rtn = DelegateThing(theDelegator->delegate, p1);
+        }
+    }
+    else 		/* no delegate */
+        rtn = DelegateThing(theDelegator->delegate, p1);
+
+    printf("%s\n", theDelegator->phrase );
+    return rtn;
+}
+
+/** * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+const char *thing1( int p1)
+{
+    printf("We're in thing1 with value %d\n" , p1);
+    return "delegate implementation";
+}
+
+int main()
+{
+    Delegate del1 = NewDelegate(&thing1);
+    Delegate del2 = NewDelegate(NULL);
+    Delegator theDelegator = NewDelegator( 14, "A stellar vista, Baby.");
+
+    printf("Delegator returns %s\n\n",
+            Delegator_Operation( theDelegator, 3, NULL));
+    printf("Delegator returns %s\n\n",
+            Delegator_Operation( theDelegator, 3, del1));
+    printf("Delegator returns %s\n\n",
+            Delegator_Operation( theDelegator, 3, del2));
+    return 0;
+}