how can i check if NSUrl is a valid image url? - iphone

Question

I'm using SDWebImage library and I have this code:
[cell.imgLogo setImageWithURL:[NSURL URLWithString:[item objectForKey:#"s_logo"]] placeholderImage:[UIImage imageNamed:#"default.png"]];
I have tweak the library SDWebImage a little bit to ignore empty string or a NSUrl with empty string in method downloadWithURL: delegate: options: userInfo::
if ([url isKindOfClass:NSString.class])
{
if ([(NSString *)url length] > 0) {
url = [NSURL URLWithString:(NSString *)url];
} else {
return;
}
}
else if (![url isKindOfClass:NSURL.class])
{
url = nil; // Prevent some common crashes due to common wrong values passed like NSNull.null for instance
}
else if ([url isKindOfClass:NSURL.class]) {
if ([[url absoluteString] length] > 0) {
//valid url
} else {
return;
}
}
So now it works with empty string and just to display its default image but the problem is when it comes to a string that is not an image url like:
http://beta.xxxxxxx.com/gangnamwe?to=boko
It displays nothing, it removes the placeholder image and displays nothing.
So how will I identify a valid image url? or is there any better work around for this?
Your help are much appreaciated.

Answer 1

you can check after getting NSData from NSURL . You can use GCD to download data
here is an example i created which save your image in photo library.
dispatch_async(dispatch_queue_create("com.getImage", NULL), ^(void) {
NSData *data=[NSData dataWithContentsOfURL:[NSURL URLWithString:#"https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcRKII9COB-hvMef4Zvb9XYVbXKDFZHJAHwwzzGyMiy_b-q65GD43Chd37jH"]];
UIImage *image=[UIImage imageWithData:data];
if (image==nil) {
//yourImageURL is not valid
image=[UIImage imageNamed:#"placeholder.png"];
}
else{
//yourImageURL is valid
dispatch_async(dispatch_get_main_queue(), ^{
UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil);
//show your image
});
}
});

Answer 2

There is method in NSURL to check if the file exsists.
- (BOOL)checkResourceIsReachableAndReturnError:(NSError **)error
Example
NSURL *theURL = [NSURL URLWithString:string];
NSError *err;
if ([theURL checkResourceIsReachableAndReturnError:&err] == NO)
{
NSLog(#"resource not reachable");
}

Answer 3

Here's a category on NSURL for you :
// nsurl+documentTypes.h
#interface NSURL (documentTypes)
- (BOOL)isImageType;
#end
// nsurl+documentTypes.m
#implementation NSURL (documentTypes)
- (BOOL)isImageType
{
NSString * UTI = (__bridge NSString *)UTTypeCreatePreferredIdentifierForTag(kUTTagClassFilenameExtension,(__bridge CFStringRef)[self pathExtension],NULL);
return UTTypeConformsTo((__bridge CFStringRef)UTI, kUTTypeImage);
}
#end

Answer 4

You can check if the url ends with some image name or not.You can get the parts of the url in following way:
NSURL* url = [NSURL URLWithString:#"http://digg.com/news/business/24hr"];
NSString* reducedUrl = [NSString stringWithFormat:
#"%#://%#/%#",
url.scheme,
url.host,
[url.pathComponents objectAtIndex:1]];
Now, take the last object of the pathComponents and check if it contains .png or .jpg etc.

Answer 5

In Swift:
import Foundation
public extension NSURL {
public var isImage: Bool {
return UTI.map{ UTTypeConformsTo($0, kUTTypeImage) } ?? false
}
public var UTI: String? {
var value: AnyObject?
let _ = try? getResourceValue(&value, forKey: NSURLTypeIdentifierKey)
return value as? String
}
}
e.g:
let url = NSURL(fileURLWithPath: "/Users/i/Desktop/image.png")
url.isImage //--> true