Re: DragNDropOutlineView Example Define Syntax
Re: DragNDropOutlineView Example Define Syntax
- Subject: Re: DragNDropOutlineView Example Define Syntax
- From: Corbin Dunn <email@hidden>
- Date: Mon, 27 Jun 2005 09:42:08 -0700
SimpleTreeNode* treeNodeItem = (SimpleTreeNode*)item;
Is this a way to cast the item as a SimpleTreeNode instance named
treeNodeItem? I don't recognize that syntax statement. Would another
of saying that be:
Yes..it is, but let me elaborate. The compiler will also accept (with
no warnings):
SimpleTreeNode* treeNodeItem = item;
Since item is type (id).
In fact, the compiler will also compile both of these without warnings:
[treeNodeItem childAtIndex:index];
[item childAtIndex:index];
So, why use the former (typed message calls) vs. the latter (untyped
id message calls)? Ultimately, the same code is generated.
Two reasons.
1. Compile time type checking
Consider this:
[treeNode stringValue];
[item stringValue];
Both items will compile, but the first line will give a warning that
"SimpleNodeData may noit respond to -stringValue" (which is true!).
The first line you could catch the error at compile time, and correct
it. If you used the second line, the problem would only come up at
runtime.
2. Code Insight
Consider this:
[treeNode |
The cursor is at the |. Press Escape (or whatever combo invokes Code
Insight / Code Sense in your Xcode -- I have mine set to ctrl-space
because it is faster to type).
What you see is a list of messages that the SimpleNodeData type
accepts. Cool; you can type down and find the one you want very quickly.
Repeat with:
[item |
What you see is a list of messages that the "id" type accepts (which
is HUGE!). It is more difficult to pick the right method that you
want to call.
--corbin
SimpleTreeNode* item = [[SimpleTreeNode alloc] initWithObject:item];
I am assuming it is a type of casting that is going on here?
Thanks again!
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Cocoa-dev mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden