Overview

Download Operation

This is a operation, subclassed from NSOperation, performs a download of a file (done atomically) that can be added to a NSOperationQueue.

Usage

1. Copy the DownloadOperation.h and DownloadOperation.m to your project and include the header file in your .m file:

    #import "DownloadOperation.h"
   

2. Create a NSOperationQueue for the download operation:

    self.downloadQueue = [[NSOperationQueue alloc] init];
   

3. Give that operation queue some reasonable maximum operation count (enjoy concurrency, but staying clear of the maximum number of network operations that iOS supports:

    self.downloadQueue.maxConcurrentOperationCount = 4;
   

4. Create a download operation:

    DownloadOperation *downloadOperation = [[DownloadOperation alloc] initWithURL:url];
   

5. Optionally, provide that operation block completion and progress blocks:

    downloadOperation.downloadCompletionBlock = ^(DownloadOperation *operation, BOOL success, NSError *error) {
        if (error) {
            NSLog(@"%s: downloadCompletionBlock error: %@", __FUNCTION__, error);
        }
        // do whatever else you want upon completion
    };
   
    downloadOperation.downloadProgressBlock = ^(DownloadOperation *operation, long long progressContentLength, long long expectedContentLength) {
        CGFloat progress = (expectedContentLength > 0 ? (CGFloat) progressContentLength / (CGFloat) expectedContentLength : (progressContentLength % 1000000l) / 1000000.0f);
        [cell.downloadProgressView setProgress:progress animated:YES];
    }
   

6. Add the operation to your operation queue to start the operation.

    [self.downloadQueue addOperation:downloadOperation];
   

7. If you need to stop an operation, you can either cancel the individual operation:

    [downloadOperation cancel];
   

   Or you can stop all of the download operations:

    [self.downloadQueue addOperation:downloadOperation];