Day 18
Day 18 관련
Project 1, part three
Now that our app is complete, it’s time for a quick recap what you learned, a short test to make sure you’ve understood what was taught, then your first challenges – exercises designed to get you writing your own code as quickly as possible.
I do not provide the answers to these challenges. This is intentional: I want you to figure it out by yourself rather than just looking at someone else’s work. Trying things out for yourself, making mistakes, and finding solutions is key to learning – as Maya Angelou once said, “nothing will work unless you do.”
Today you should work through the wrap up chapter for project 1, complete its review, then work through all three of its challenges.
Wrap up
Wrap up
This has been a very simple project in terms of what it can do, but you've also learned a huge amount about Swift, Xcode and storyboards. I know it's not easy, but trust me: you've made it this far, so you're through the hardest part.
To give you an idea of how far you've come, here are just some of the things we've covered: table views and image views, app bundles, FileManager, typecasting, view controllers, storyboards, outlets, Auto Layout, UIImage, and more.
Yes, that's a huge amount, and to be brutally honest chances are you'll forget half of it. But that's OK, because we all learn through repetition, and if you continue to follow the rest of this series you'll be using all these and more again and again until you know them like the back of your hand.
Review what you learned
Anyone can sit through a tutorial, but it takes actual work to remember what was taught. It’s my job to make sure you take as much from these tutorials as possible, so I’ve prepared a short review to help you check your learning.
Click here to review what you learned in project 1.
Challenge
This has the beginnings of a useful app, but if you really want your new knowledge to sink in you need to start writing some new code yourself – without following a tutorial, or having an answer you can just look up online.
So, each time you complete a project I’ll be setting you a challenge to modify it somehow. Yes, this will take some work, but there is no learning without struggle – all the challenges are completely within your grasp based on what you’ve learned so far.
For this project, your challenges are:
Use Interface Builder to select the text label inside your table view cell and adjust its font size to something larger – experiment and see what looks good. In your main table view, show the image names in sorted order, so “nssl0033.jpg” comes before “nssl0034.jpg”. Rather than show image names in the detail title bar, show “Picture X of Y”, where Y is the total number of images and X is the selected picture’s position in the array. Make sure you count from 1 rather than 0.
Hints
It is vital to your learning that you try the challenges above yourself, and not just for a handful of minutes before you give up.
Every time you try something wrong, you learn that it’s wrong and you’ll remember that it’s wrong. By the time you find the correct solution, you’ll remember it much more thoroughly, while also remembering a lot of the wrong turns you took.
This is what I mean by “there is no learning without struggle”: if something comes easily to you, it can go just as easily. But when you have to really mentally fight for something, it will stick much longer.
But if you’ve already worked hard at the challenges above and are still struggling to implement them, I’m going to write some hints below that should guide you to the correct answer.
If you ignore me and read these hints without having spent at least 30 minutes trying the challenges above, the only person you’re cheating is yourself.
Still here? OK. Let’s take a look at the challenges…
Use Interface Builder to select the text label inside your table view cell and adjust its font size to something larger – experiment and see what looks good.
This ought to be easy enough: open Main.storyboard, then use the document outline to select the table view, select the Picture cell inside it, select the Content View inside that, and finally select the Title label. In the attributes inspector you’ll find a number of options – try to figure out which one controls the font size.
In your main table view, show the image names in sorted order, so “nssl0033.jpg” comes before “nssl0034.jpg”.
These pictures may or may not already be sorted for you, but your challenge here is to make sure they are always sorted. We’ve covered sorting arrays previously, and you should remember there’s a sort() method you can use.
However, the question is: where should it be called? You could call this method each time you append an “nssl” picture to the pictures array, but that just causes extra work. Where could you put a call to sort() so its done only once, when the images have all been loaded?
Rather than show image names in the detail title bar, show “Picture X of Y”, where Y is the total number of images and X is the selected picture’s position in the array. Make sure you count from 1 rather than 0.
In this project you learned how to create properties like this one:
var selectedImage: String?
You also learned how to set those properties from somewhere else, like this:
vc.selectedImage = pictures[indexPath.row]
This challenge requires you to make two new properties in DetailViewController: one to contain the image’s position in the array, and one to contain the number of pictures.
For example, you might add these two properties to DetailViewController:
var selectedPictureNumber = 0
var totalPictures = 0
You can then use those for the title in the navigation bar by using string interpolation. Remember, string interpolation looks like this:
title = "This image is \(selectedImage)"
How can you use that with selectedPictureNumber and totalPictures?
Once that’s done, you need to pass in some values for those properties. We create DetailViewController here:
override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
if let vc = storyboard?.instantiateViewController(withIdentifier: "Detail") as? DetailViewController {
vc.selectedImage = pictures[indexPath.row]
navigationController?.pushViewController(vc, animated: true)
}
}
That sets the selectedImage property using one of the strings from the pictures array. Which string? Well, we use indexPath.row for that, because that tells us which table view cell was selected.
So, we can use indexPath.row to set the selectedPictureNumber property in DetailViewController – just make sure you add 1 to it so that it counts from 1 rather than 0.
As for the totalPictures property in DetailViewController, which needs to contain the total number of pictures in our array. We already wrote code to read the size of the array inside the numberOfRowsInSection method – how can you use similar code to set totalPictures?
Wrap up - Additional
Once you’re done, tell other people: you’ve completed your first iOS project, you’ve passed the test, and you’ve even extended it with your own code.
You should be proud of what you’ve accomplished – good job!