Dependency injection

- [Instructor] Dependency injection has got to be … one of the most annoying terms in all of programming. … It describes something that is so blatantly obvious, … we don't even know we're doing it. … Let's look at what dependency injection is … and what it is used for. … If you download the example file, you'll find a playground. … I have two classes here. … We have the pizza class, … uses the size class to get a size. … Put another way, pizza has a dependency of size. … I set initial values for height and width. … So if you run this, … this'll work fine just as it is, … but right now it would only give me an area of 120. … If I want to change the height or width, … I have to make an initializer for size. … So I would go into here and do an init … and then do height double and then width, double. … And then of course self dot height equals height … and self dot width equals width. … Okay, and you'll see … that we get a missing arguments down here. … So I can go ahead and now change those around …