On Dec 29, 2011, at 3:38 PM, Peter Teeson wrote:
> I'm familiarizing myself with Xcode 4.2.1 under Lion 10.7.2 so am doing the
> "Your First Mac App" tutorial.
>
> This code snippet from the tutorial is incorrect and causes an error in
> compilation.
> if (sender == textField) { senderName = @"textField"; }…….
> The error is "Use of undeclared identifier 'textField'; did you mean
> _textField?"
>
> The correct code is:
> if (sender == self.textField){senderName = @"textField"; }
>
> In fact if you refer to any of the synthesized iVars such as 'window' or
> 'slider'
> or indeed any that you care to make up for yourself (eg aardvark) the same
> issue occurs.
>
> I don't know if this is a scope, language or compiler issue.
> Why would one need to use self.textField?
This is just an issue with the tutorial. Those properties are @synthesized
with an explicit instance variable name, which is different from the property
name due to the underscore prefix:
@synthesize textField = _textField;
You don't necessarily have to refer to "self.textField". You could have
changed that line to be:
if (sender == _textField){senderName = @"textField"; }
The problem with the original is that it referred to an identifier "textField"
which didn't correspond to any declared variable. The instance variable is
called "_textField". And property names are not accessible just as naked
identifiers; they need to be accessed using Dot Syntax (or, of course, using
the getter or setter names or Key-Value Coding).
It was good of you to give that feedback to the document maintainers.
Cheers,
Ken
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