How to check the PDF size before uploading in iOS?

Question

I have a requirement of uploading PDF file which is not more than 2 MB. Right now I am using the UIDocumentPickerViewController to browse the PDF files. Is there any way to check whether the PDF's size is larger than 2 MB? I am able to get the size using NSByteCountFormatter. The code is given below:

NSData *fileData = [NSData dataWithContentsOfURL:url];
NSLog(@"Byte Length%@", [[NSByteCountFormatter new] stringFromByteCount:fileData.length]);
NSString *twoMB = [[NSByteCountFormatter new] stringFromByteCount:fileData.length];
NSString *allowedmem = @"2 MB";
if (twoMB > allowedmem) {
    NSLog(@"Greater than 2 MB");
} else {
    ViewMyPDFViewController *webview = [[ViewMyPDFViewController alloc]init];
    webview.productURL = url;
    [self presentViewController:webview animated:YES completion:nil];
}

I have tried this code but it is not working well in the if condition. Please tell what I am doing wrong. How do I check whether it is greater than 2 MB?

shim · Accepted Answer · 2020-09-01T15:29:21.193

You are comparing two strings in this expression inside the if condition:

twoMB > allowedmem

This is doing an alphabetical comparison rather than a numerical one. In some cases this might happen to give you the correct result anyway (e.g. "3 MB" > "2 MB" => true) but in many cases it wouldn't (e.g. "300 kB" > "2 MB" => true).

You do not need NSByteCountFormatter as you already have the number of bytes. Simply check if the number of bytes exceeds 2 MB. For example, compare it to 2E6:

NSData *fileData = [NSData dataWithContentsOfURL:url];
NSUInteger pdfBytes = fileData.length;
NSUInteger allowedBytes = 2e6; // 2 MB is 2 million bytes, or 2 x 10 ^ 6
if (pdfBytes > allowedBytes) {
    NSLog(@"Greater than 2 MB");
} else {
    ViewMyPDFViewController *webview = [[ViewMyPDFViewController alloc]init];
    webview.productURL = url;
    [self presentViewController:webview animated:YES completion:nil];
}

Note that these contexts typically use a binary system, so 2 MB is actually 2,097,152 bytes if you want to be more exact. There are more robust methods of comparison involving formatters as you have shown but you should be careful to do a numeric and not an alphabetic comparison regardless of which method you use. You may also find it useful to create a file which you know is 2 MB in size, and get its .length after loading it in, and just using whatever number you get there for the comparison.

thanks for the idea .. can you please help me with how to check if the number of bytes exceeds 2 MB? — User1075, Sep 01 '20 at 15:01

How to check the PDF size before uploading in iOS?

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