doubleValue (for an NSString)
doubleValue (for an NSString)
- Subject: doubleValue (for an NSString)
- From: Boyd Collier <email@hidden>
- Date: Fri, 21 Mar 2008 18:54:34 -0700
First, thanks to everyone who suggested ways to handle this. Next, an
admission of guilt for faulty memory; mine, not my Mac's: in poking
around, I discovered that I'd asked pretty much the same question (for
ints) nearly 2 years ago and had gotten similar answers. My apologies.
I've decided to use a scanner, and, as a couple of you said, it's
really rather simple. But I was concerned about whether using
something like
[[NSScanner scannerWithString:aString] scanDouble:&distance];
when, in some situations, I will be scanning for potentially thousands
of values within a loop, and so I presumed that this would cause an
equal number of scanners to accumulate in the default autorelease
pool. Is that correct? So I tried
NSScanner *tempScanner = [[NSScanner alloc] initWithString:aString];
[tempScanner scanDouble:&distance];
[tempScanner release];
in a loop, wondering if all the allocations and releases would slow
things down. The result was that scanning for 10000 values took only
about 8 milliseconds on my 2.8 GHz iMac, which is plenty fast enough
for my purposes.
Any further comments, even ones telling me that I should take up
knitting instead of programming, are welcome.
Boyd
On Mar 20, 2008, at 4:13 PM, Boyd Collier wrote:
According to Apple's documents, the selector doubleValue returns 0.0
if the instance of an NSString that is the receiver "doesn’t begin
with a valid text representation of a floating-point number." Is
there a simple way to distinguish between the string 0.0, which
shouldn't be considered illegitimate for my purposes, and the string
(for example) X0.0 other than writing extra lines of code to
distinguish one case from the other? I know I could use a scanner,
but perhaps there's something simple that I'm overlooking.
Boyd_______________________________________________
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