Re: *?
Re: *?
- Subject: Re: *?
- From: jgo <email@hidden>
- Date: Fri, 22 Jun 2001 17:56:43 -0700
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I keep running into things like:
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NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
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and:
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- (NSString *)airports;
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- (void)setAirports:(NSString *)str;
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Now, I understand the use of the * in:
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NSMutableArray *myArray;
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which says that myArray is of type "NSMutableArray" instead of generic
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type "id". But there is no explanation that I can find as to what the *
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does or means in the first two examples. My copy of Kernighan and
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Ritchie just came and I looked there, but all I could find was a usage
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somewhat similar on page 94 that uses the * to indicate that an argument
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is a pointer to a type. So, all I can guess is that in the example:
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- (NSString *)airports;
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the * is shorthand for statically typing "airport" to NSString. Is that
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right? If so, then in the second line:
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- (void)setAirports:(NSString *)str;
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"str" is statically typed to NSString also?
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As for the first example:
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NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
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is this the same as:
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NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];?
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Is the space between the * and "pool" optional? If so is there some
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reason to use the extra space in this construction?
Yes. In general a declaration with a * in it means the variable is a
pointer to something of the type designated (as you found in K&R), so
char * fred;
means that fred is a pointer to char, and the space for char is
usually dynamically allocated using fred = new char or
fred = new char[sizeOfCharString]
(or in OS 9- for unsigned char * fred it would be
fred = NewPtr(sizeOfCharString)) or the equivalent.
In Objective-C all "static" declarations of objects are
NSQuark * thisobject;
because, in practice, instances of objects are blocks of memory
pointed to by the variable.
If you look in the docs or _LC_ pg 29, for example, you'll see
id [is] an object (a pointer to [an object's] data structure)
and then on page 76 you see that "Generic outlets are declared as:
IBOutlet id variableName;" while their modified "static" equivalent
is "IBOutlet NSTextField * textField;"
There are at least 3 schools on spacing the * in such declarations:
type* var;
type *var;
type * var;
John G. Otto Nisus Software, Engineering
www.infoclick.com www.mathhelp.com www.nisus.com software4usa.com
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Will program Macs for food.
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