LoadOperation.m

/*
     File: LoadOperation.m 
 Abstract: NSOperation code for examining image files.
  
  Version: 1.3 
  
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 */
 
#import "LoadOperation.h"
 
// key for obtaining the current scan count
NSString *kScanCountKey = @"scanCount";
 
// key for obtaining the path of an image fiel
NSString *kPathKey = @"path";
 
// key for obtaining the size of an image file
NSString *kSizeKey = @"size";
 
// key for obtaining the name of an image file
NSString *kNameKey = @"name";
 
// key for obtaining the mod date of an image file
NSString *kModifiedKey = @"modified";
 
// NSNotification name to tell the Window controller an image file as found
NSString *kLoadImageDidFinish = @"LoadImageDidFinish";
 
@interface LoadOperation ()
{
    NSURL *loadURL;
    NSInteger ourScanCount;
}
 
@property (retain) NSURL *loadURL;
 
@end
 
 
@implementation LoadOperation
 
@synthesize loadURL;
 
// -------------------------------------------------------------------------------
//  initWithPath:path
// -------------------------------------------------------------------------------
- (id)initWithURL:(NSURL *)url scanCount:(NSInteger)scanCount
{
    self = [super init];
    if (self)
    {
        self.loadURL = url;
        ourScanCount = scanCount;
    }
    return self;
}
 
// -------------------------------------------------------------------------------
//  isImageFile:filePath
//
//  Uses LaunchServices and UTIs to detect if a given file path is an image file.
// -------------------------------------------------------------------------------
- (BOOL)isImageFile:(NSURL *)url
{
    BOOL isImageFile = NO;
    
    NSString *utiValue;
    [url getResourceValue:&utiValue forKey:NSURLTypeIdentifierKey error:nil];
    if (utiValue)
    {
        isImageFile = UTTypeConformsTo((__bridge CFStringRef)utiValue, kUTTypeImage);
    }
    return isImageFile;
}
 
// -------------------------------------------------------------------------------
//  main:
//
//  Examine the given file (from the NSURL "loadURL") to see it its an image file.
//  If an image file examine further and report its file attributes.
//
//  We could use NSFileManager, but to be on the safe side we will use the
//  File Manager APIs to get the file attributes.
// -------------------------------------------------------------------------------
- (void)main
{
    if (![self isCancelled])
    {
        // test to see if it's an image file
        if ([self isImageFile:loadURL])
        {
            // in this example, we just get the file's info (mod date, file size) and report it to the table view
            //
            NSNumber *fileSize;
            [self.loadURL getResourceValue:&fileSize forKey:NSURLFileSizeKey error:nil];
            
            NSDate *fileCreationDate;
            [self.loadURL getResourceValue:&fileCreationDate forKey:NSURLCreationDateKey error:nil];
            
            NSDateFormatter* formatter = [[NSDateFormatter alloc] init];
            [formatter setTimeStyle:NSDateFormatterNoStyle];
            [formatter setDateStyle:NSDateFormatterShortStyle];
            NSString *modDateStr = [formatter stringFromDate:fileCreationDate];
            
            NSDictionary *info = [NSDictionary dictionaryWithObjectsAndKeys:
                                  [self.loadURL lastPathComponent], kNameKey,
                                  [self.loadURL absoluteString], kPathKey,
                                  modDateStr, kModifiedKey,
                                  [NSString stringWithFormat:@"%ld", [fileSize integerValue]], kSizeKey,
                                  [NSNumber numberWithInteger:ourScanCount], kScanCountKey,  // pass back to check if user cancelled/started a new scan
                                  nil];
            
            if (![self isCancelled])
            {
                // for the purposes of this sample, we're just going to post the information
                // out there and let whoever might be interested receive it (in our case its MyWindowController).
                //
                [[NSNotificationCenter defaultCenter] postNotificationName:kLoadImageDidFinish object:nil userInfo:info];
            }
        }
    }
}
 
@end