Function Injection example

injectionexample.swift

//: Playground - noun: a place where people can play

import Foundation
import UIKit

class ImageProcessor {
    let postProcessOp:(UIImage) -> ()

    init(postProcessOp:@escaping (UIImage) -> () = {_ in })  {
        self.postProcessOp = postProcessOp
    }

    func processImage(original: UIImage) -> UIImage {
        let image = original.imageFlippedForRightToLeftLayoutDirection()
        postProcessOp(image)
        return image
    }
}

class Factory {
    func validImageProcessor() -> ImageProcessor {
        return ImageProcessor(postProcessOp: Cacher.saveCachedImage)
    }
}

class Cacher {
    static func saveCachedImage(image:UIImage) {
        print("Feeling sick today - Won't cache anything")
    }
}