[iOS] 也许是使用最方便的图片下载扩展及 ImageView 加载类库

Moa, an image downloader written in Swift for iOS, tvOS and macOS

Moa is an image download library written in Swift. It allows to download and show an image in an image view by setting its moa.url property.

imageView.moa.url = "https://bit.ly/moa_image"

• Images are downloaded asynchronously.
• Uses URLSession for networking and caching.
• Allows to configure cache size and policy.
• Can be used without an image view.
• Provides closure properties for image manipulation and error handling.
• Includes unit testing mode for faking network responses.
• Contains logging capabilities for debugging network problems.

'Hunting Moa' drawing by Joseph Smit (1836-1929). File source: Wikimedia Commons .

Setup (Swift 3.0)

There are three ways you can add Moa to your Xcode project.

Add source (iOS 7+)

Simply addMoaDistrib.swift file into your Xcode project.

Setup with Carthage (iOS 8+)

Alternatively, add github "evgenyneu/moa" ~> 4.0 to your Cartfile and run carthage update .

Setup with CocoaPods (iOS 8+)

If you are using CocoaPods add this text to your Podfile and run pod install .

use_frameworks! target 'Your target name' pod 'moa', '~> 4.0' 

Legacy Swift versions

Setup aprevious version of the library if you use an older version of Swift.

Usage

import moa UIImageView moa.url 

imageView.moa.url = "https://bit.ly/moa_image"

Loading images from insecure HTTP hosts

If your image URLs are not https you will need to add an exception to the Info.plist file. This will allow the App Transport Security to load the images from insecure HTTP hosts.

Canceling download

Ongoing image download for the image view is automatically canceled when:

1. Image view is deallocated.
2. New image download is started: imageView.moa.url = ... .

Call imageView.moa.cancel() to manually cancel the download.

Supply an error image

You can supply an error image that will be used if an error occurs during image download.

imageView.moa.errorImage = UIImage(named: "ImageNotFound.jpg") imageView.moa.url = "https://bit.ly/moa_image"

Alternatively, one can supply a global error image that will be used for all failed image downloads.

Moa.errorImage = UIImage(named: "ImageNotFound.jpg")

Show a placeholder image

Here is how to show a placeholder image in the image view. The placeholder will be replaced by the image from the network when it arrives.

imageView.image = placeholderImage imageView.moa.url = "https://bit.ly/moa_image"

Advanced features

Supplying completion closure

Assign a closure that will be called when image is received.

imageView.moa.onSuccess = { image in   return image }  imageView.moa.url = "https://bit.ly/moa_image"

• The closure will be called after download finishes and before the image is assigned to the image view.
• This is a good place to manipulate the image before it is shown.
• The closure returns an image that will be shown in the image view. Return nil if you do not want the image to be shown.
• The closure as called in the main queue . Use onSuccessAsync property instead if you need to do time consuming operations.
• When errorImage is supplied and an error occurs the success closures are called.

Supplying error closure

imageView.moa.onError = { error, response in   // Handle error }  imageView.moa.url = "https://bit.ly/moa_image"

• The closure is called in the main queue if image download fails. Use onErrorAsync property instead if you need to do time consuming operations.
• Use error.localizedDescription to get a human-readable error description.

Download an image without an image view

An instance of Moa class can also be used without an image view. A strong reference to Moa instance needs to be kept.

let moa = Moa() moa.onSuccess = { image in   // image is loaded   return image } moa.url = "https://bit.ly/moa_image"

Clearing HTTP session

The following method calls finishTasksAndInvalidate on the current URLSession object. A new session object will be created for future image downloads.

MoaHttpSession.clearSession()

You may never need to call this method in your app. I needed to call it periodically to workaround a strange URLSession bug which you may not encounter.

Image caching

Use the Moa.settings.cache to change caching settings. For more information please refer to the moa image caching manual .

// By default images are cached according to their response HTTP headers. Moa.settings.cache.requestCachePolicy = .useProtocolCachePolicy  // Always cache images locally regardless of their response HTTP headers Moa.settings.cache.requestCachePolicy = .returnCacheDataElseLoad

Settings

Use Moa.settings property to change moa image download settings.

// Set the maximum number of simultaneous image downloads. Default: 4. Moa.settings.maximumSimultaneousDownloads = 5  // Change timeout for image requests. Default: 10. Moa.settings.requestTimeoutSeconds = 20

Logging

You can use the moa logger to see how/when the images are loaded or debug a network problem. One can use a pre-made MoaConsoleLogger function to see the log messages in the Xcode console or write a custom logger. See thelogging manual for more information.

// Log to console Moa.logger = MoaConsoleLogger  // Load an image imageView.moa.url = "https://bit.ly/moa_image"  // Attempt to load a missing image imageView.moa.url = "https://bit.ly/moa_image_missing.jpg"

Unit testing

Sometimes it is useful to prevent code from making real HTTP requests. Moa includes MoaSimulator class for testing image downloads and faking network responses. Seeunit test manual for more information.

// Autorespond with the given image to all image requests MoaSimulator.autorespondWithImage("www.site.com", image: UIImage(named: "35px.jpg")!)

Demo app

The demo iOS app shows how to load images in a collection view with Moa.

Alternative solutions

Here is the list of other image download libraries for Swift.

• cbot/Vincent
• daltoniam/Skeets
• Haneke/HanekeSwift
• hirohisa/ImageLoaderSwift
• natelyman/SwiftImageLoader
• onevcat/Kingfisher
• zalando/MapleBacon

Credits

• Demo app includes other drawings by Joseph Smit. Source: Wikimedia Commons .

• macOS support is added byphimage.

License

Moa is released under theMIT License.

Feedback is welcome

If you notice any issue, got stuck or just want to chat feel free to create an issue. I will be happy to help you.

•ᴥ•

This project is dedicated to the moa , species of flightless birds that lived in New Zealand and became extinct in 15th century.