Re: ObjC question
Re: ObjC question
- Subject: Re: ObjC question
- From: Quincey Morris <email@hidden>
- Date: Mon, 21 Feb 2011 13:07:11 -0800
On Feb 21, 2011, at 12:19, Tony Romano wrote: I'm trying to do this:
-(void) insert: (BTreeNode **) node node:(BTreeNode *) n { …
// get the address of the left member [self insert:&[(*node) left] node:n]; // <--- error }
The compiler(GCC 4.2 or LLVM 1.6) is giving this error : address _expression_ must be an lvalue or a function designator.
I was assuming the return value for [[(*node) left]] is a lvalue (it's a pointer) and I should be able to obtain the address of that pointer but either you can't or the value returned from the message call to node is not a lvalue.
You're all tangled up. A return value is *never* a lvalue (if it was, you could write 'sqrt (4) = 3;'), so you're going to have to do this:
BTreeNode *temp = [(*node) left]; [self insert:&temp node:n];
but your code is still very smelly because it's not clear why you're passing around a pointer to the pointer to the left node (BTreeNode **). If the intention is to have 'insert:node:' return the left node pointer to its caller, why not just use a return value?
BTW, this the wrong list for this question, since it's not about Xcode. The correct list is probably email@hidden.
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