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Delegates: Difference between revisions
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delegate implementation
</pre>
=={{header|C}}==
As best you can do, without support for classes.
<lang c>#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef char * (*Responder)( int p1);
typedef struct sDelegate {
Responder operation;
} *Delegate;
/* Delegate class constructor */
Delegate NewDelegate( Responder rspndr )
{
Delegate dl = (Delegate)malloc(sizeof(struct sDelegate));
dl->operation = rspndr;
return dl;
}
/* Thing method of Delegate */
char *DelegateThing(Delegate dl, int p1)
{
return (dl->operation)? (*dl->operation)(p1) : NULL;
}
/** * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
typedef struct sDelegator {
int param;
char *phrase;
Delegate delegate;
} *Delegator;
char * defaultResponse( int p1)
{
return "default implementation";
}
static struct sDelegate defaultDel = { &defaultResponse };
/* Delegator class constructor */
Delegator NewDelegator( int p, char *phrase)
{
Delegator d = (Delegator)malloc(sizeof(struct sDelegator));
d->param = p;
d->phrase = phrase;
d->delegate = &defaultDel; /* default delegate */
return d;
}
/* Operation method of Delegator */
char *Delegator_Operation( Delegator theDelegator, int p1, Delegate delroy)
{
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;
}
/** * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
char *thing1( int p1)
{
printf("We're in thing1 with value %d\n" , p1);
return "delegate implementation";
}
int main(int argc, char*argv[])
{
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;
}</lang>
=={{header|Common Lisp}}==
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