EMAsyncImageView

Yet another asynchronous, web-enabled, internet-friendly, download-and-cache UIImageView subclass.

This one will put up a UIActivityIndicatorView into its superview while it waits for the image to download. It will also handle both full url static paths to images, and query urls that fetch images based on an arbitrary image id parameter (see usage notes).

There are also provisions for handling multiple image sizes of the same image id.

A sample app is included.

Feedback is welcome!

Installation:

1 Copy the 2 files in the EMAsyncImageView folder and add them to your project:

* EMAsyncImageView.h
* EMAsyncImageView.m

2 Add this line to any class header or implementation file where you reference an EMAsyncImageView

* #import "EMAsyncImageView.h"

or, for convenience's sake, add that line to your [project]-Prefix.pch file

Example usage:

In a UICollectionView:

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {

	GalleryCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"cell" forIndexPath:indexPath];
	cell.picView.imageUrl = [picsArray objectAtIndex:indexPath.row];
	return cell;
}

where GalleryCell.h contains:

#import "EMAsyncImageView.h"

@interface GalleryCell : UICollectionViewCell {
}

@property (weak, nonatomic) IBOutlet EMAsyncImageView 	*picView;

@end

If this view is contained in a reusable cell, such as in a UITableView or UICollectionView, add:

- (void)prepareForReuse {
	[super prepareForReuse];
	picView.imageUrl = nil;
}

Sample App

You'll need to download this entire repo for the sample app to work, as the EMAsyncImageView.xcodeproj references both the EMAsyncImageView and Sample_App top level folders (plus the snazzy 30-minute-photoshop-hack app icons).

Usage notes:

The following is noted in EMAsyncImageView.h:

Setting the imageUrl or imageId properties will immediately start the download or fetch the cached image from the file system.
Set the imageId property if you already have it. Otherwise, setting the imageUrl property will attempt to generate the imageId from the url, for caching purposes.
If using this class in a resuable cell, such as UICollectionViewCell or UITableViewCell, it is highly recommended to set imageUrl to nil in -prepareForReuse:
- (void)prepareForReuse { [super prepareForReuse]; picView.imageUrl = nil; }
Special thanks to Illya Busigin (illyabusigin) and Jason Pepas (cellularmitosis) for this and other great tweaks.
Note that setting imageUrl to nil signals that the view is being used in a reusable cell, and so will not use iOS image caching (file system cache still works though).
EMAsyncImageView can process both full static urls to images, or query urls to retrieve images based on an image id parameter.

If the url is a query of the form:
```
  http://domain.com/api/getImage?userid=abc&arbritraryidkey=123
```
them specifying the imageIdKey property (to "arbritraryidkey" in this example) will enable caching of the image to the file system.
If imageIdKey is not set, the image will be downloaded upon every request.
But wait! If the parameter name happens to be "imageId", and imageIdKey is not set, then that will still cache the image. Convention over configuration, as it were.
And yet, go head and change the defaultImageIdKey #define below to set your own convention. Sigh.

License

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.