DAY 9
Closures
Brace yourself, because today we’re covering the first thing in Swift that many people have a hard time understanding. Please keep in mind Flip Wilson's law: “you can't expect to hit the jackpot if you don't put a few nickels in the machine.”
Today the topic is closures, which are a bit like anonymous functions – functions we can create and assign directly to a variable, or pass into other functions to customize how they work. Yes, you read that right: passing one function into another as a parameter.
Closures are really difficult. I’m not saying that to put you off, only so that you know in advance if you’re finding closures hard to understand or hard to remember, it’s okay – we’ve all been there!
Sometimes the syntax for closures can be a bit hard on your eyes, and this will really be apparent as you work through today’s lessons. If you find it a bit overwhelming – if you’re staring at some code and aren’t 100% sure of what it means – just go back one video and watch it again to give your memory a little nudge. You’ll find there are more tests and optional reading links than usual below, hopefully helping to solidify your knowledge.
SwiftUI uses closures extensively so it’s worth taking the time to understand what’s going on here. Yes, closures are probably the most complex feature of Swift, but it’s a bit like cycling up a hill – once you’ve reached the top, once you’ve mastered closures, it all gets much easier.
Today you have three tutorials to follow, plus a summary and another checkpoint. As always once you’ve completed each video there’s some optional extra reading and short tests to help make sure you’ve understood what was taught. This time you’ll notice there’s quite a bit of each of those because closures really can take some time to understand, so don’t be afraid to explore!
- How to create and use closures
- Optional: What the heck are closures and why does Swift love them so much?
- Optional: Why are Swift’s closure parameters inside the braces?
- Optional: How do you return a value from a closure that takes no parameters?
- Test: Creating basic closures
- Test: Accepting parameters in a closure
- Test: Returning values from a closure
- How to use trailing closures and shorthand syntax
- How to accept functions as parameters
- Optional: Why would you want to use closures as parameters?
- Test: Closures as parameters
- Test: Trailing closure syntax
- Summary: Closures
- Checkpoint 5
That’s another key Swift topic under your belt – good job! Now do the smart thing and post your progress online: it forces you to write about these things in your own words, and also encourages you to continue on to tomorrow.
Still not sure about closures?
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100 Days of SwiftUI
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