Hi ! A while back there was a brief discussion about the relative merits of passing an object parameter directly vs passing it as a pointer. As I remember, the conclusion was that a pointer wasn’t needed because 4D is just passing a reference to the object - it isn’t copying the object in the called method as it would do for, say, a text field.
So I proceeded to do object library code just passing the object reference directly to save on dereferencing pointers etc. However, now I’ve realised a huge problem with this approach which is that it isn’t portable. For example, as soon as you use the code in a component it breaks because 4D can no longer reference the object across the component-host boundary. Not only that, even if you pass the object to the component as a pointer, ANY further use if the dereferenced object pointer as a parameter in a subsequent method call will fail. So, lets say you have a library method that does this: ===== myObjectMethod === C_OBJECT($1) …and you use that anywhere in a component, it will always fail if its argument ultimately originated in a host. (Whereas it wouldn’t fail in a host-only call). This is actually consistent behaviour with other data types when you think about it, but what isn’t consistent is that the other data types wouldn’t work in the host either whereas objects do. (i.e. when you pass an object directly as a method argument, any processing on the object will be reflected in the calling method’s scope as well which would not be the case for, say, a text value). CONCLUSION ==================== My inclination is to conclude that passing objects directly is not very good practice at all because it doesn’t result in consistent behaviour with other data types and isn’t portable. Worse, it makes the code difficult to audit if you use components because it only takes a single call to break an entire call chain that would otherwise perform 100% under test, either in a host environment or when unit testing the component. To get consistent and portable behaviour we’d have to do this: myMethod(OB Copy($object)) <— to behave like a classic parameter pass where the data is duplicated in the called method or mtMethod(->$object) <— to behave like a classic pointer, where the source data is processed and not duplicated in the called method but not myMethod($object) <— Iceberg waiting for Titanic ==================== What do other people think about this ? Is anyone else bothering about this distinction ? Best Regards Peter ********************************************************************** 4D Internet Users Group (4D iNUG) FAQ: http://lists.4d.com/faqnug.html Archive: http://lists.4d.com/archives.html Options: http://lists.4d.com/mailman/options/4d_tech Unsub: mailto:[email protected] **********************************************************************
