Question

I am attempting to create an application that goes through various images from the net and aim to cache them onto the iPhone for offline use. The code I am currently working with is:

NSMutableDictionary *Cache;
- (UIImage *)CachedImage: (NSString*)url {
    UIImage *image = [Cache objectForKey:url];
if (image == nil) {
    image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:url]]];
    [Cache setObject:image forKey:url];
    //NSLog (@"Stored");
    return image;
} else {
    //NSLog (@"Taken");
    return image;
} }

I call the function and place the image into an ImageView using the strip of code below.

    [self.imageView setImage:[self CachedImage:url]]; // Change url to desired URL.

Using the NSLog, the problem I found is that the code doesn’t actually store the value because the value is always reading nil. Why is that and are there other ways of storing images for offline use?
Thanks in advance.

-Gon

Answer 1

Use NSCache to cache UIImages. You can also save the image locally (if you reuse these images a lot and during multiple launch) so whenever your app closes or you flush your cache, you can get the images immediately from your local directory.

https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/NSCache_Class/Reference/Reference.html