On 2009-02-02 21:19:52 -0500, Daniel Keep <[email protected]> said:
Michel Fortin wrote:
[stuff]
Wouldn't this be just as well served with Walter's "universal function
syntax"; ie:
void backup(File this, string backupPath)
{
copy(this.path, backupPath ~ "/" ~ this.name);
}
File someFile;
someFile.backup(backupPath);
It would work in your example, but not in mine. Note the difference:
foreach(child; children)
child.backup(backupPath ~ "/" ~ this.name);
Statically, child is a Node here. If at runtime child is a File, the
backup function is overriden by the FileBackup extension of File, so
it'd call the backup function from FileBackup, not NodeBackup. If at
runtime child is a Directory, it'll call DirectoryBackup's backup
function. At least, that's what it would do in Objective-C using
categories. And that's why you don't need the visitor pattern in
Objective-C.
--
Michel Fortin
[email protected]
http://michelf.com/
