Re: NSEnumerator and the missing peek method

• Subject: Re: NSEnumerator and the missing peek method
• From: Marcel Weiher <email@hidden>
• Date: Fri, 30 Sep 2005 00:20:34 +0100
• Delivered-to: email@hidden
• Delivered-to: email@hidden

On 29 Sep 2005, at 22:27, Jan Vereecken wrote:

That is the solution I use at the moment. I was only wondering if someone maybe found a way to extend NSEnumerator with a new method to peek which would make following code possible.

while(myObject = [enumerator nextObject]) {
    do something (for example append a string)
    if([enumerator hasNext]) {
        do something (for example add a newline)
    }
}

@interface PeekingEnumerator : NSEnumerator
    NSEnumerator *sourceEnumerator;
    id    peekedObject;
}

-initWithSourceEnumerator:(NSEnumerator*)anEnumerator;
-(BOOL)hasNextObject;
-peek;

@end

@interface NSEnumerator(makePeekable)

-(PeekingEnumerator*)peekable;

@end

@implementation PeekingEnumerator

-initWithSourceEnumerator:(NSEnumerator*)anEnumerator
{
    self = [super init];
    [self setSourceEnumerator:anEnumerator];
    return self;
}

idAccessor( peekedObject, setPeekedObject )
objectAccessor( NSEnumerator* , sourceEnumerator, setSourceEnumerator )

-initWithSourceEnumerator

-sourceNextObject
{
    return [sourceEnumerator nextObject];
}

-peek
{
    if ( ![self peekedObject] ) {
        [self setPeekedObject:[self sourceNextObject]];
    }
    return [self peekedObject];
}

-nextObject
{
    id returnValue = [[[self peek] retain autorelease];
    [self setPeeked:nil];
    return returnValue;

}

-hasNextObject
{
    return [self peek] != nil;
}

-(void)dealloc
{
    [peekedObject release];
    [sourceEnumerator release];
    [super dealloc];
}

-(PeekingEnumerator*)peekable
{
    return self;
}

@end

@implementation NSEnumerator(makePeekable)

@end

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