iOS Loading images in UITableViewCell with RAC - ios

Question

Am just starting with RAC and am wondering how to load images asynchronously in a cell within a TableView.
I was trying with the example in the doc, but to be honest, I didn't understand so well...
The thing is that the project is written with RAC, so I want to do the right things.
What have I tried?:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"tableCell";
CustomTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
cell.elementName.text = self.myListOfElements[indexPath.row].elementName;
RAC(cell.imageView, image) = [[finalImage map:^(NSURL *url) {
return [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:self.myListOfElements[indexPath.row].url]]];
}] deliverOn:RACScheduler.mainThreadScheduler];
}
But this is not working...
Does anybody know the proper way to do this with RAC?

Answer 1

I have never used RAC, but based on the examples it looks you are referencing a URL that you do not seem have.
RAC(self.imageView, image) =
[
[
[
[
client fetchUserWithUsername:#"joshaber"
]
deliverOn:[RACScheduler scheduler]
]
map:^(User *user) {
// Download the avatar (this is done on a background queue).
return [[NSImage alloc] initWithContentsOfURL:user.avatarURL];
}
]
// Now the assignment will be done on the main thread.
deliverOn:RACScheduler.mainThreadScheduler
];
In the example this section:
[
[
client fetchUserWithUsername:#"joshaber"
]
deliverOn:[RACScheduler scheduler]
]
-fetchUserWithUsername is the function that returns the User object that contains the URL used to download the image.

Answer 2

This line assumes that there is already a UIImageView object created and set on the CustomTableViewCell's imageView property:
RAC(cell.imageView, image) = [[finalImage map:^(NSURL *url) {
Presumably this UIImageView object is being created in the CustomTableViewCell class's initializer or in -prepareForReuse method. If it's not, that could be part of your problem.
Be aware, though, that this code doesn't look that safe. If a CustomTableViewCell instance is reused, then you could end up calling RAC(cell.imageView, image) on the object a second time, which would be a problem. (On the other hand, if -prepareForReuse is creating a new UIImageView each time, then this shouldn't be a problem.)