What is the difference between UIImage(named:) and UIImage(imageLiteralResourceName:)?

Question

Swift 3/iOS 10 added a new initializer on UIImage, imageLiteralResourceName:

extension UIImage {

    required public convenience init(imageLiteralResourceName name: String)
}

How does this differ from public init?(named name: String)? I named is a failable initializer while imageLiteralResourceName will crash on an invalid image name. Does imageLiteralResourceName trade safety for performance? When should you use imageLiteralResourceName over named?

Answer 1

Looking at the open-source implementation of UIKit, there seems to be no difference:

extension UIImage : _ImageLiteralConvertible {
  private convenience init!(failableImageLiteral name: String) {
    self.init(named: name)
  }

  public required convenience init(imageLiteralResourceName name: String) {
    self.init(failableImageLiteral: name)
  }
}

public typealias _ImageLiteralType = UIImage

All it does is force-unwrap the result of init(named:).

It seems like it's just an implementation of the _ImageLiteralConvertible protocol found in CompilerProtocols.swift :

public protocol _ImageLiteralConvertible {
  init(imageLiteralResourceName path: String)
}

AppKit also has a similar implementation:

extension NSImage : _ImageLiteralConvertible {
  private convenience init!(failableImageLiteral name: String) {
    self.init(named: name)
  }

  public required convenience init(imageLiteralResourceName name: String) {
    self.init(failableImageLiteral: name)
  }
}

public typealias _ImageLiteralType = NSImage

This might have to do with the new image literal functionality (#imageLiteral) added to Xcode 8 and should never be called directly.