Using Enumerations Part 3

Loading...

En provenance du cours de University of California, Irvine

Toward the Future of iOS Development with Swift

74 notes

Explorer les vidéos de cours associées

Vous trouverez chez Coursera les meilleures vidéos de cours du monde. Voici quelques-unes de nos recommandations personnalisées pour vous

University of California, Irvine

Toward the Future of iOS Development with Swift

74 notes

Cours 5 sur 6 dans Specialization iOS Development for Creative Entrepreneurs

An introduction to the Swift programming language. This will prepare you for more extensive iOS app development and build a foundation for advanced iOS development topics. Upon completing this course, you will be able to: 1. Associate the relationship of Swift and Objective-C and their use in iOS and Mac (OS X) programming 2. Develop the ability to read and write Swift code 3. Distinguish how both programming languages can be used together in applications 4. Demonstrate how to write applications entirely in Swift with the help from several iOS programming samples 5. Determine how Swift can be used for development on new platforms such as Apple Watch and Apple TV 6. Create a working client-server iPhone application with location services that you can add to your portfolio.

À partir de la leçon

Looking Further into Swift

The content for this week will build on the knowledge and examples from the previous week. You will start combining the basic programming skills studied in the previous week to start manipulating data in functions and learn how functions can be used in different Types (i.e. enums, structs, classes). This will prepare you for working in a full application setting, which will be the focus of Week 4. You will learn about some of the more advanced Swift programming language features that are often useful in bringing together a complete system like a full-blown iPhone application.

How to Create Basic Enumerations7:25

How to Create Raw-Value Enumerations8:48

Using Enumerations Part 111:17

Using Enumerations Part 25:33

Using Enumerations Part 37:35

Enumerations Methods and Limitations4:26

Rencontrer les enseignants

Justin-Nicholas Toyama
UCI Extension Instructor
Lead iOS Developer at Smilefish Corporation
Frank Ayars
UCI Extension Instructor
CTO and Director of Software Development at Smilefish Corporation
Ralf Brockhaus
UCI Extension Instructor
Founder and CEO at Smilefish Corporation

[MUSIC]

All right, so now we can do things like call that property, or

call the methods on the enum type.

So here I have MilkyWayPlanet.Earth.order.

And notice how properties and functions of enum types are called using

dot syntax just as we expect for any other type like we've been working with.

So we know that Earth is the third planet away, and we kept this zero index.

So, zero, one, two, is the third planet and indeed, over here on the right hand

side, we see its order is 2, so that's good, that's what we expect.

Now we can say, let firstPlanet, of type MilkyWayPlanet = .Mercury.

Notice how we were able to just say .Mercury instead of

having to say MilkyWayPlanet.Mercury, because we explicitly typed this

constant called firstPlanet, as of type MilkyWayPlanet.

Also note how, even though in this playground we have

our MilkyWayPlanet enum, and we also have our Planet enum.

If we come back down here, notice how we have

a case called Mercury on both of those enums.

Even though we have two Mercurys in this playground, or

two Mercurys in this scope because we defined the type

as being of type MilkyWayPlanet, it will know which

enum type .Mercury this instance is associated with.

Let's just take a quick look, if I cut this away and

don't explicitly type firstPlanet then I'm going to get an error.

And the compiler would complain,

type of expression is ambiguous without more context.

Because it needs to know is this the planet .Mercury or MilkyWayPlanet.Mercury?

So if I replace the explicit typing then the compiler knows which one to use.

Okay, and same thing here with just saying let

thirdPlanet = .Earth, we get the same complaint.

Okay, so let me comment that back out.

Let's take a look now at how we can call those methods that we

defined on the MilkyWayPlanet enum.

So in our earlier examples, we had to do a lot of work and

long functions to list out the names of the moons.

because our planets existed as dictionaries.

We had to go first see if there was a moon's array inside of

the planet dictionary.

Then we'd have to go iterate over all of the moons and

turn those into proper English sentences, etc.

And that was a lot of code typing that we had to do.

Here, we've listed out the moons in a much simpler fashion.

Maybe not as nice English sentences, but with a lot less typing,

we can show the moon count and show the moon names.

So here I just a do a simple for loop and

I've created an array of the MilkyWayPlanets called theMilkyWay.

And here I've populated an array with a bunch of different Milky Way planets.

And I say for planet in theMilkyWay, even though I know that

our planets are just one solar system in the Milky Way, but let's just

go ahead with this example because I had to call it something different.

So for planet in theMilkyWay planet.showMoonCount( ) and

planet.showMoonNames( ).

Now over here on the right-hand side it's not actually going to do that because

there's sort of not enough space for it to do it in line with each line of code.

So, we have to go look at our console for that.

So, I'm going to click this middle button here up in the right hand corner where you

see three buttons together, and it says hide or show the debug area.

So, that will bring my console up at the bottom and I'll drag this up so

we have a little bit more space to see what's going on.

And here we have for planet in theMilkyWay, planet.showMoonCount.

And keep in mind, showMoonCount just shows us, prints out the number of moons,

and showMoonNames which prints out a list of the moon names.

So here we see.

We're going to start off with Mercury and, of course, we know Mercury has no moons.

So we get showMoonCount, 0, showMoonNames, no moons.

Same thing for Venus as the next one in the order, 0 moons, no moons.

Now we get to Earth, one moon and it's called Luna, and we go ahead and

we go down all the list of planets in our array called theMilkyWay and

we can see the number of moons and the list printed out.

So our code's working as expected.

All right, I wanted to show you again one more time,

we typically might not do this because it's not very expressive.

Here, our code is very expressive, we have an array, and

we can clearly see the planets inside of our array, Mercury, Venus, Earth, etc.

But these planets also have an integral value associated with them, so

I could have said, let orderedSolarSystem equal zero, one, two, three,

four, five, six, seven.

And this is maybe expressive in a different way,

it's not as easy to see the name of the planet that

we're talking about in code, but we can see which

planet is it in terms of order of distance from the sun.

So now I can create planets out of

these Ints using the init with raw value initializer we saw earlier.

So now I can say for planet in orderedSolarSystem, so

that's the name of this array.

MilkyWayPlanet init with rawValue,

the planet which is again, going to be an Int because this

is the value that it's getting out of the array as it iterates over the array.

Now I've created a planet and if I was successful in creating a planet with

a valid rawValue, then I will have a valid instance of the planet.

Whatever the case may be.

Now I can ask it, .showMoonCount, and

that will work out just fine down here in the console.

[MUSIC]

Explorer notre catalogue

Rejoignez-nous gratuitement et obtenez des recommendations, des mises à jour et des offres personnalisées.

Coursera propose un accès universel à la meilleure formation au monde, en partenariat avec des universités et des organisations du plus haut niveau, pour proposer des cours en ligne.

© 2019 Coursera Inc. Tous droits réservés.

Télécharger dans l'App Store

Disponible sur Google Play