CODEWITHSUNDEEP
iphoneobjective-ccocoa
Eileen Sauer
Eileen Sauer

Reputation: 25

Cocoa: I can sort by filename, how do I sort by file extension?

Here is my answer:

-(IBAction)sortBySelectedFilter {
    ...
    [self sortWithKey:@"filename" ascending:ascending selector:@selector(compareFileType:)];
    ...
}

-(void)sortWithKey:(NSString *)name ascending:(BOOL)asc selector:(SEL)sel {
    NSSortDescriptor *byKey = [[[NSSortDescriptor alloc] initWithKey:name
                                                           ascending:asc
                                                            selector:sel] autorelease];
    self.fileNames = [NSMutableArray arrayWithArray:[self.fileNames sortedArrayUsingDescriptors:[NSArray arrayWithObject: byKey]]];
    ...
}

@interface NSString (FileExtension) 

- (NSComparisonResult)compareFileType:(NSString *)filename;

@end

#import "NSString+FileExtension.h"

@implementation NSString (FileExtension)

-(NSComparisonResult)compareFileType:(NSString *)filename {
    return [[NSString stringWithFormat:@"%@, %@", [self pathExtension], [self stringByDeletingPathExtension]]
            compare:
            [NSString stringWithFormat:@"%@, %@", [filename pathExtension], [filename stringByDeletingPathExtension]]];
}

@end

Upvotes: 0

Views: 287

Answers (1)

Joshua Nozzi
Joshua Nozzi

Reputation: 61238

You haven't mentioned whether you're using Core Data or SQLite directly. With Core Data, you can use a custom NSManagedObject subclass (remember to set the class in the Managed Object Model). This subclass would have an -(NSString *)extension method that asks self for -valueForKey:@"filename" and returns just the extension of the file name (using NSString's -pathExtension method). Then change your sort key to "extension" and it should work.

Note: If you're using Core Data and the SQLite store type, you won't be able to fetch or otherwise query using this method, since it doesn't really exist as an attribute in your store.

If you're not using Core Data, I assume your object already has its own class, so it should be obvious how to add your -extension method.

Upvotes: 1

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