Question

Possible Duplicate:
Cannot create PDF document with 400+ pages on iOS

My app generates PDF files. These PDf’s can be large due to the user being able to add pages, potentially unlimited, although usual is approx. 10. Im having problems with iPhone 4 users experiencing a crash at the PDF genration stage. Some investigative work shows the app is running out of memory during the PDF generation stage, I get low memory warnings then final crash. I can reproduce the problem If I add 50 plus pages on iPhone 5, a lot less on iPhone 4, and not on the simulator which is expected.

Can anyone suggest how I can reduce this aculamitive memory climb and ultimate crash when generating the PDf file.

Ive researched SO: iPhone App Crashes due to Low Memory but works fine in simulator and Quartz PDF API Causing Out of Memory Crashes

@interface ICPDFPreviewController ()
@property (nonatomic, strong) Certificate *certificate;
@property (nonatomic, strong) NSData *pdfData;
@property (nonatomic) BOOL viewHasUnloaded;
- (void)generatePdf;
- (void)pdfDone:(NSData *)data;
- (NSData *)createPdfWithPages:(NSArray *)pages;
@end

@implementation ICPDFPreviewController
@synthesize certificate=_certificate;
@synthesize scrollView=_scrollView;
@synthesize webView=_webView;
@synthesize pdfData=_pdfData;
@synthesize viewHasUnloaded=_viewHasUnloaded;



- (void)generatePdf
 {
 NSMutableArray *pagesArray = [NSMutableArray array];

 if ([self.certificate.certificateType.title isEqualToString:@"Minor Works"]) {
[pagesArray addObject:[[ICPDFMinorWorksPage1 alloc] initWithCertificate:self.certificate]];
[pagesArray addObject:[[ICPDFMinorWorksPage2 alloc] initWithCertificate:self.certificate]];

} else if ([self.certificate.certificateType.title isEqualToString:@"EIC"]) {
[pagesArray addObject:[[ICPDFEICPage1 alloc] initWithCertificate:self.certificate]];
[pagesArray addObject:[[ICPDFEICPage2 alloc] initWithCertificate:self.certificate]];
[pagesArray addObject:[[ICPDFEICPage3 alloc] initWithCertificate:self.certificate]];
[pagesArray addObject:[[ICPDFEICPage4 alloc] initWithCertificate:self.certificate]];
[pagesArray addObject:[[ICPDFEICPage5 alloc] initWithCertificate:self.certificate]];
[self addDistributionBoardsToPagesArray:pagesArray];
ICPDFEICPageFinal *pageFinal = [[ICPDFEICPageFinal alloc] initWithCertificate:self.certificate];
pageFinal.pageNumber.text = [NSString stringWithFormat:@"%d", pagesArray.count+1];
[pagesArray addObject:pageFinal];

} else if ([self.certificate.certificateType.title isEqualToString:@"Domestic EIC"]) {
[pagesArray addObject:[[ICPDFDomesticEICPage1 alloc] initWithCertificate:self.certificate]];
[pagesArray addObject:[[ICPDFDomesticEICPage2 alloc] initWithCertificate:self.certificate]];
[pagesArray addObject:[[ICPDFDomesticEICPage3 alloc] initWithCertificate:self.certificate]];
[pagesArray addObject:[[ICPDFDomesticEICPage4 alloc] initWithCertificate:self.certificate]];
[self addDistributionBoardsToPagesArray:pagesArray];
[pagesArray addObject:[[ICPDFDomesticEICPageFinal alloc] initWithCertificate:self.certificate]];

} else if ([self.certificate.certificateType.title isEqualToString:@"EICR"]) {
[pagesArray addObject:[[ICPDFEICRPage1 alloc] initWithCertificate:self.certificate]];
[pagesArray addObject:[[ICPDFEICRPage2 alloc] initWithCertificate:self.certificate]];
[self addObservationsToPagesArray:pagesArray];
[self addDistributionBoardsToPagesArray:pagesArray];
[pagesArray addObject:[[ICPDFEICRInspection alloc] initWithCertificate:self.certificate]];
[pagesArray addObject:[[ICPDFEICRInspectionPage1 alloc] initWithCertificate:self.certificate]];
[pagesArray addObject:[[ICPDFEICRInspectionPage2 alloc] initWithCertificate:self.certificate]];
[pagesArray addObject:[[ICPDFEICRInspectionPage3 alloc] initWithCertificate:self.certificate]];
[pagesArray addObject:[[ICPDFEICRPageFinal alloc] initWithCertificate:self.certificate]];
 }

// Set page count on all pages
int pageNumber = 0;
for (ICCertificateComponent *page in pagesArray) {
page.pageNumber.text = [NSString stringWithFormat:@"%d", ++pageNumber];
page.pageCount.text = [NSString stringWithFormat:@"%d", pagesArray.count];
}

NSData *pdfData = [self createPdfWithPages:pagesArray];
[self performSelectorOnMainThread:@selector(pdfDone:) withObject:pdfData waitUntilDone:YES];

 }

- (void)pdfDone:(NSData *)data
{
self.pdfData = data;
[self.webView loadData:self.pdfData MIMEType:@"application/pdf" textEncodingName:@"utf-8"   baseURL:nil];
[ICUtils removeProgressView];
}

- (NSData *)createPdfWithPages:(NSArray *)pages
 {
// Creates a mutable data object for updating with binary data, like a byte array
NSMutableData *pdfData = [NSMutableData data];

 ICCertificateComponent *firstPage = [pages objectAtIndex:0];

UIGraphicsBeginPDFContextToData(pdfData, firstPage.contentView.bounds, nil);

 for (int i = 0; i < pages.count; i++) {
ICCertificateComponent *thisPage = [pages objectAtIndex:i];
UIGraphicsBeginPDFPageWithInfo(thisPage.contentView.bounds, nil);
    ////////////////////////////////////////////////////////////////////
   //tried adding this after research on SO, did not stop app crash
  // CGContextSetInterpolationQuality((__bridge CGContextRef)(thisPage), kCGInterpolationHigh);    CGContextSetRenderingIntent((__bridge CGContextRef)(thisPage), kCGRenderingIntentDefault);
 /////////////////////////////////////////////////////////////////////

CGContextRef pdfContext = UIGraphicsGetCurrentContext();
[thisPage.contentView.layer renderInContext:pdfContext];
}

UIGraphicsEndPDFContext();

return pdfData;
}

- (void)addDistributionBoardsToPagesArray:(NSMutableArray *)pagesArray
{
int pageCount = pagesArray.count;
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"createdAt"    ascending:YES];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil]; 
NSArray *boards = [self.certificate.distributionBoards   sortedArrayUsingDescriptors:sortDescriptors];
for (DistributionBoard *thisBoard in boards) {
DebugLog(@"Creating a board page");
ICPDFDistributionBoard *boardPage = [[ICPDFDistributionBoard alloc]   initWithDistributionBoard:thisBoard];
boardPage.pageNumber.text = [NSString stringWithFormat:@"%d", ++pageCount];
DebugLog(@"Page number is %d", pageCount);
[pagesArray addObject:boardPage];

NSSortDescriptor *circuitDescriptor = [[NSSortDescriptor alloc] initWithKey:@"createdAt" ascending:YES];
NSArray *circuitDescriptors = [[NSArray alloc] initWithObjects:circuitDescriptor, nil]; 
NSArray *circuits = [thisBoard.circuits sortedArrayUsingDescriptors:circuitDescriptors];

//int circuitCount = circuits.count;
ICPDFCircuitDetails *circuitDetails = boardPage.circuitDetails;

int circuitCount = 0;
for (Circuit *thisCircuit in circuits) {
    circuitCount++;
    if (circuitCount > 16) {
        // Add an extension page
        DebugLog(@"Adding an extension sheet");
        circuitCount = 1;
        ICPDFDistributionBoardExtension *boardExtension = [[ICPDFDistributionBoardExtension  alloc] initWithDistributionBoard:thisBoard];
        [pagesArray addObject:boardExtension];
        boardExtension.pageNumber.text = [NSString stringWithFormat:@"%d", ++pageCount];
        circuitDetails = boardExtension.circuitDetails;
     }
    NSString *key = [NSString stringWithFormat:@"circuitRow%d", circuitCount];
    ICCircuitRow *circuitRow = [circuitDetails valueForKey:key];
    [circuitRow populateFromCircuit:thisCircuit];
    }
  }
  }

Answer 1

In general, memory is finite and your generated output isn’t, so the way to make it work is to ensure that:

• you’re not accumulating the entire PDF in memory as you generate it
• you’re not unnecessarily keeping around byproducts of the rendering for each page

In your case, using UIGraphicsBeginPDFContextToData means that you’re rendering the whole PDF to an ever-expanding NSData. When that data gets too big, you’ll get killed. Instead, try UIGraphicsBeginPDFContextToFile. Also in your inner loop for rendering pages, consider inserting an @autoreleasepool { ... } block to prevent objects from building up unnecessarily during a long run. I’m not sure how big your pagesArray bunch of stuff actually is, and whether that’s something you might consider “paging in” one page at a time as you generate.