Swift lazy load property Alamofire request - ios

Question

I'm trying to lazy load a property (UIImage) with an Alamofire request. This is where I'm at:
public lazy var theImage: UIImage = MyCalass.loadImage { (imageTest) -> Void in
return imageTest
}
class public func loadImage(completion: (imageTest: UIImage) -> Void){
Alamofire.request(.GET, "http://pathtoimage/image.jpg").response { (request, response, data, error) in
var tempImage = UIImage(data: data!, scale:1)
completion(imageTest: tempImage!)
}
}
Error on the : '()' is not convertible to 'UIImage'

Answer 1

Hey man its easy to solve with GCD...
Just build up a Class like this:
class AsynchImageLoader {
class func loadImageAsync (imageURL: NSURL, completionHandler: (downloadedImage: UIImage?) -> Void) {
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), { () -> Void in
if let imageData: NSData = NSData(contentsOfURL: imageURL) {
if let imageImage: UIImage = UIImage(data: imageData) {
dispatch_async(dispatch_get_main_queue(), { () -> Void in
completionHandler(downloadedImage: imageImage)
})
} else {
dispatch_async(dispatch_get_main_queue(), { () -> Void in
completionHandler(downloadedImage: nil)
})
}
} else {
dispatch_async(dispatch_get_main_queue(), { () -> Void in
completionHandler(downloadedImage: nil)
})
}
})
}
}
And than load your Images like this...
let imageView: UIImageView = UIImageView()
AsynchImageLoader.loadImageAsync(NSURL(string: "yourURL")!, completionHandler: { (downloadedImage) -> Void in
imageView.image = downloadedImage
})
downloadedImage could be nil, if something went wrong... otherwise you could put it into your view, or an array, or whatever you want...
By the way... The lazy modifier doesn't mean that the image is loaded "lazy/async"... In Swift you can declare / initialize something as lazy what means that it will be declared on init of its class, but it will first be initialized shortly before you firstly try to access it in code... That could be any time, or even never :-)
Or change your Code from this...
public lazy var theImage: UIImage = MyCalass.loadImage { (imageTest) -> Void in
return imageTest
}
To this...
var theImage: UIImage?
MyCalass.loadImage { (imageTest) -> Void in
theImage = imageTest
}

Answer 2

If you're working with Images, I recommend you to use something like DLImageLoader, it can be installed with CocoaPods, for loading an image just use
DLImageLoader.sharedInstance().displayImageFromUrl("\(thumbnailUrl)", imageView: myImageView)
This way your image is loaded when the download has finished, also check the other options, there are some with callbacks, but the above example is the simplest
And it even uses cache if you need the image several times in your app, I have an implementation of it and works nice, and I have Alamofire also. I came to this complement once I replaced AFNetworking which used to have this kind of image download management

Answer 3

You don't have to use Alamofire to load in an image. You can make it async though.
You could do something like this, closure included:
lazy var theImage: UIImage = {
var sampImage = getImage({ (image) in
return image
})
}()
func getImage(completion: UIImage -> ()) {
var newImage: UIImage?
let priority = DISPATCH_QUEUE_PRIORITY_DEFAULT
dispatch_async(dispatch_get_global_queue(priority, 0)) {
let url = NSURL(string: "http://pathtoimage/image.jpg")
let data = NSData(contentsOfURL: url!)
newImage = UIImage(data: data!)!
completion(newImage!)
}
}
EDIT: I was able to successfully load an image in a Playground file using this code below. The problem before was that the request was async which for some reason lead to it not returning properly.
import UIKit
class Example {
lazy var theImage: UIImage = {
var newImage: UIImage?
let url = NSURL(string: "http://2.bp.blogspot.com/-XJbC3jA7cOo/VW2ItW5aRjI/AAAAAAAACcc/_f_WhTEXvFQ/s1600/testPattern.png")
let data = NSData(contentsOfURL: url!)
newImage = UIImage(data: data!)!
println(data)
return newImage!
}()
init() {}
}
var exp = Example()
exp.theImage
I'm thinking that function calls aren't allowed in lazy loaded properties