Swift 4 download file from url

So I need my download function works even when the app goes into background. If you need to download only text file into String you can use this simple way, Swift 3 :.

You should know that network operations may take some time, to prevent it from running in main thread and locking your UI, you may want to execute the code asynchronously, for example:. Yes you can very easily downloads Files from the remote Url Using this code. This Code is working Fine for Me. I already am able to fetch the url from the Api which is in Json format. But this one is the image url. I have. In JSON all the image url are coming. I can see it. Now how to download image from that url and show in collection view.

Please tell anyone how can I apply here. It's not definitive, but check out this meta post. Show 1 more comment. Active Oldest Votes. The image will continue downloading in the background and it will be loaded when it ends.

Leo Dabus Leo Dabus k 55 55 gold badges silver badges bronze badges. Just a side note here, you should set an associated object to it; Otherwise you might load images on top of each other. If process 1 takes longer then process 2, process 2 will show its image and it will then later be updated by process 1 even though that image is no longer valid for the user.

PaulPeelen could you add more info about how this would be done? It would be great if we could make this awesome answer even better. The first one downloads to memory the second one to a file — Leo Dabus.

Show 31 more comments. Data contentsOf: url! Lucas Eduardo Lucas Eduardo Perhaps you can update your answer? I still do not agree. Some answers should be kept simple, a lot of people that comes here likes to copy and paste small snippets of code.

I just translated to Swift the objective-C code from the original question, everything besides that is a bonus. And by the way, there is already a answer in this same question providing this kind of bonus information, which makes less sense to duplicate information.

User just replace the image. IanWarburton Of course you can use whatever you want :. Heyo, the suggested framework, kingfisher, as stated in the answer will do all of the heavy lifting. Thanks for the suggestion! Show 11 more comments. It is not showing up, and I think because there is a need for GCD.

How do I refresh? Check your bindings with view. Thanks skywinder, I am using this method for downloading images from array. I want when user press on cancel button it stops downloading. Have you any idea how i can do this with using this method?

I've need to add cancel functionality. Swift 3: foregroundImage. Thanks, mate, this helped me. Add a comment. Mark Moeykens Mark Moeykens Swift 4: : This will shows loader while loading the image. Jack Jack It works. Just copy activityIndicator removal in error case too. ScaleAspectFill self. Do we really need those overridden inits?

Aren't the inits inherited anyway? Seems like we're just overriding here just to call super on itself, which strikes me as redundant. String if url! UIImage data: data! Manee ios Manee ios 1, 10 10 silver badges 14 14 bronze badges. Anonymous 9, 2 2 gold badges 20 20 silver badges 38 38 bronze badges. Any chance you can write up something asynchronous?

I had to unwrap the NSData with an "! If we read the docs carefully , it becomes clear that data task is NOT the right candidate for downloading big assets. That class is designed to request only smaller objects, since the underlying data is going to be loaded into memory. On the other hand the download task saves the content of the response on the disk instead of memory and you will receive a local file URL instead of a Data object.

Turns out that moving from data tasks to download tasks will have a HUGE impact on your memory consumption. I have some numbers. I made a brand new storyboard based Swift 5.

Here's a quick summary:. I hope you get my point. Please don't forget that the Foundation networking layer comes with four types of session tasks. You should always use the right one that fits the job. You might say that this is an edge case since most of the images even HD ones are maximum a few hundred kilobytes. Still, my takeaway here is that we can do better, and we should always do so if possible. Modern times require modern APIs, right? If you are already familiar with the new SDK that's good, but if you don't know what the heck is this declarative functional reactive madness, you should read my comprehensive tutorial about the Combine framework.

Wait, where are the others? No download task publisher? What should we do now? Another great read even better than the first one by Donny Wals is about understanding Publishers and Subscribers. It's a really well-written article, you should definitely check this one, I highly recommend it.

Now let's start creating our own DownloadTaskPublisher. There is also a DataTaskPublisher struct, right below. Based on that template we can create our own extension. There are two variants of the same data task method, we'll replicate this behavior. The other thing we need is a DownloadTaskPublisher struct, I'll show you the Swift code first, then we'll discuss the implementation details.

A Publisher can send an Output or a Failure message to an attached subscriber. You have to create a new typealias for each type, since they both are generic constraints defined on the protocol level. Next, we'll store the session and the request objects for later use.

This method is responsible for attaching a new subscriber through a subscription object. A Publisher and a Subscriber is connected through a Subscription. The Publisher only creates the Subscription and passes it to the subscriber. The Subscription contains the logic that'll fetch new data for the Subscriber.