On 12 Jul 2009, at 10:16 AM, William Squires wrote:
- (void)setWebView:(SomeAppDelegate *)appDelegate
{
NSString *htmlString;
htmlString = @"<div style=\"font-family;Helvetica,Arial, sans-serif;
font-size=48pt;\"align=\"center\">";
htmlString = [htmlString
stringByAppendingString:appDelegate.savedNumber];
htmlString = [htmlString stringByAppendingString:@"</span>"];
[webView loadHTMLString:htmlString baseURL:nil];
// [htmlString release]; // <- is this necessary?
}
Two issues.
First, the release you've commented-out is not only unnecessary, it is
wrong. The value that htmlString holds is not a literal string, but
the computed result of the method -[NSString
stringByAppendingString:]. By the rules, you don't have ownership of
that object, and must not release it.
(You're balancing a <div> with a </span>, but I assume that's just a
typed-in-mail typo.)
Second, your nominal question about retaining/releasing literal
strings. In practice, you don't have to use the ownership pattern on
them. They are kept as constant objects in the binary, and memory-
management methods on them are no-ops. I confess I take advantage of
this in my own code.
I really shouldn't. Code that starts with the assumption that I don't
have to manage them will fail when I change it to use strings that
have to be managed. If the memory-management methods are no-ops on
literals, they also do no harm. Therefore I should do:
myInstanceVariable = [@"literal" copy];
...
[myInstanceVariable release];
-or-
@property(copy) NSString * myProperty;
...
self.myProperty = @"literal";
...
self.myProperty = nil; // Pace the debate on whether
// and when this should be
// release-and-set-nil.
Now, don't get nuts over this. You shouldn't retain/copy a literal
string in contexts where you wouldn't do the same for any other object.
— F
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