App crashes if null image URL is loaded in JSON object - ios

Question

I am populating a tableView with objects from a MySQL table via JSON.
The source data are introduced by many users in a web site form, and sometimes they don't introduce an image URL into a field.
The downloaded JSON object are shown in the tableView which rows are configured to show text, detail text and image.
If the object doesn't have an image URL, the app crashes, and I want to show a default image instead, to avoid the crash.
This is how am I loading the JSON data for the object's image:
NSMutableString *logo = [[NSMutableString alloc]initWithString:#"http://mujercanariasigloxxi.appgestion.eu/logos/"];
NSString *imageURL = [[categorias objectAtIndex:indexPath.row] objectForKey:#"strImagen"];
[logo appendString:imageURL];
NSURL *logoURL = [NSURL URLWithString:logo];
NSData *logoData = [NSData dataWithContentsOfURL:logoURL];
cell.imageView.image = [UIImage imageWithData:logoData];
What should be the best way to avoid the crash and to show a default image if the web site user doesn't include an image URL in the web form?

Answer 1

Try use a if-else condition, like
NSMutableString *logo = [[NSMutableString alloc]initWithString:#"http://mujercanariasigloxxi.appgestion.eu/logos/"];
NSData *logoData;
if([categorias objectAtIndex:indexPath.row] && [[categorias objectAtIndex:indexPath.row] objectForKey:#"strImagen"]){
NSString *imageURL = [[categorias objectAtIndex:indexPath.row] objectForKey:#"strImagen"];
[logo appendString:imageURL];
NSURL *logoURL = [NSURL URLWithString:logo];
logoData = [NSData dataWithContentsOfURL:logoURL];
}
else {
//load your default image here
logoData = //default logo data
}
cell.imageView.image = [UIImage imageWithData:logoData];

Answer 2

//set an activity indicator
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0ul);
dispatch_async(queue, ^{
NSString *imageURL = [[categorias objectAtIndex:indexPath.row] objectForKey:#"strImagen"];
if (imageURL.count>0){
[logo appendString:imageURL];
//declare logodata as nsdata
logoData=[NSData dataWithContentsOfURL:[NSURL URLWithString:logo]];
}
dispatch_sync(dispatch_get_main_queue(), ^{
//turn the activity indicator off
if(logoData!=nil)
cell.imageView.image = [UIImage imageWithData:logoData];
else
//set your default image.
});
});
Hope this might help you.

Answer 3

You may try checking whether imageurl is nil or in some cases it will come as null.
NSMutableString *logo = [[NSMutableString alloc]initWithString:#"http://mujercanariasigloxxi.appgestion.eu/logos/"];
NSString *imageURL = [[categorias objectAtIndex:indexPath.row] objectForKey:#"strImagen"];
if(imageURL != nil && ![imageURL isEqual:[NSNull null]])
{
[logo appendString:imageURL];
NSURL *logoURL = [NSURL URLWithString:logo];
NSData *logoData = [NSData dataWithContentsOfURL:logoURL];
cell.imageView.image = [UIImage imageWithData:logoData];
}
else{
cell.imageView.image = [UIImage imageNamed:#"Default_image"];
}