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In the last few lessons, we've managed to create a Weather Manager object which is able to perform the
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networking that fetches the live data from OpenWeather Map,
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and then we're able to pass the weather into an actual Swift object which we can access in a Swifty
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format like this.
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In this lesson, I want to focus on getting hold of our weather conditions because we need to be able
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to update this image view with a different image from the system's
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SF icons, so that it represents the condition of the weather.
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Now, if we take a look at the API doss for OpenWeather, you can see that they've got this section on
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list of condition code. And this section here links to all of the condition codes that they use, and that
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refers to the ID property in the data that we get back.
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What do these IDs actually correspond to?
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Well, they're a way of encoding different weather conditions.
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So, for example, everything from 200 to 232, encode some sort of thunderstorm, and there's
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apparently different types of thunderstorms which I didn't really know about,
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like a ragged thunderstorm. I don't want to be in one of those.
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Now, we know that we can get hold of the ID which is the ID of the weather condition and we can match
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it against these values to see what type of image we should show the user.
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So let's go ahead and do that. Instead of getting hold of the description which we're not actually gonna
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use,
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instead, I'm going to change this property to "id" and the "id" is an integer data type. And I can do
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this because the "id" is actually nested inside at the same level as the description.
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So changing that over from the description to the "id" or you can if you want to just simply added on
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as an additional property if you plan on using the description at some later stage. But they both live
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within this Weather struct which is an array of weather conditions that we're getting back which comes
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from the entire WeatherData.
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So following it down, this is the first property which goes into an array, which then has an object with
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a property code "id."
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So quite convoluted, but eventually, we should be able to get a hold of this number.
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Let's go ahead and try to print that in our WeatherManager just to make sure that it's actually working.
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So let's see what it's like in Bali at the moment. And the weather condition code I'm getting back is
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803.
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And if I check against this table 803 is broken clouds, 51 to 84 percent.
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Interesting.
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So in this case, I would probably just show a cloud in my app right here.
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So this is the perfect opportunity to utilize what you've learned about Swift switch statements a few
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modules back.
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So I'm going to set this to you as a challenge. Given that we have this ID which I'll call 
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let id = decodedData.weather [0].id,
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I want you to create a function down here that we'll call
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getConditionName, and it takes the input in the format of the weatherId which is going to be an integer,
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and then inside this function, we're going to return a String. And that string will depend on the Weather
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ID.
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So we're going to call this getConditionName and pass in the id right here that we get back,
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and then inside this method was somehow going to use a switch statement to output a string, and that string
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should match the name of one of these symbols.
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So, for example, if we were getting clouds, then maybe we would simply return the word "cloud" which would
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match with this image's name.
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And if we got, say, rain then maybe we would put cloud.rain to get this symbol. Because, eventually,
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what we're going to do is we're going to be using that condition name to change this image view here.
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So if we got cloud.rain as the condition name, that's what we would see. If we got just a cloud,
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then we would get this image. If we got sun.max, then we would get this image.
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So feel free to pick and choose whichever icon takes your fancy as long as they more or less match the
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condition name that we're getting back from Open Weather Maps table.
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And then when you get this condition name back, I want you to go ahead and print it, so that when you
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run the app and you put in the name of a location, say in Paris, and you go ahead and get the weather
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for it, you should be able to get a name for a SF symbol that matches the weather condition of that
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location.
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Now, if you already know all about the Swift switch statements and you don't want to complete this challenge,
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then you can also head over to the README file and you'll find the switch statement already written
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for you. But I recommend that more practice is always good.
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So using a Switch statement, try and print out the name of an icon that matches the condition ID from
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OpenWeather Map.
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I'm going to leave it up to you to pause the video and complete the challenge if you want to. All right.
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So here's our Switch statement. And it looks at the weatherID that we get passed over and takes a
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look at its value, and tries to match it against these cases, and these cases I've put in as ranges.
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So the range between 200 and 232 in the weather condition codes matches a thunderstorm.
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So out of all of these pictures of thunderstorms, I think the cloud.bolt looks quite nice.
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So I've decided to return cloud.bolt, and I've done basically the same thing to match all of these
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different conditions.
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And in the default condition where none of these cases match, then I'm just gonna return cloud as the
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default option.
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Now, if you are at all confused about Switch statements or the range operator, then be sure to head back
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to some of those Swift Deep Dives where we talked about those things in more detail. And that's the solution
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to the challenge. But now you might be noticing that this file is getting a little bit messy and we're
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getting to the point where we kind of need to group some data in a custom data type. And that is, of course,
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the role of the data model.
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So let's do that now.
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Let's reorganize our code in accordance with the MVC design pattern.
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This means that we'll take some functionality out of the WeatherManager and put it into a separate
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file.
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That way, we'll have shorter and simpler files that are easier to understand. If I want to create a custom
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weather data model which is able to figure out the condition name based on the condition ID, then I
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would need to go into my Model folder and create a New File which I'm going to call the WeatherModel,
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and I'm gonna use this file to model what a weather object should look like.
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Let's create it as a struct and it's gonna be called a WeatherModel and it's gonna have a number of
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properties.
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So we definitely need to have a conditionId property which is an Int.
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We also need to have a city name property which is gonna be a String.
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And finally, we also need a temperature property which is gonna be a Double.
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So now I can go ahead and move this functionality of figuring out what the condition name should be
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based on the condition code or the weatherId.
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This is very much within the realm of the weather object.
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So let's go ahead and paste that in here.
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Now, back inside our Weather Manager. Instead of having all these disparate pieces of information, I can
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create my ID as my decodedData weatherId. I can create my temperature or temp as the
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decodedData.main.temp.
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And finally, I'm gonna create my city name or I'm just gonna call it name for short
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from the decodedData.name property.
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So, now that I've got all the properties that I want out of my weather data, I can create myself a weather
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object from my new WeatherModel.
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So when we initialize it, we have provide the conditionId which is the ID, the cityName which is
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name, and the temperature which is temp.
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Now, if I wanted to get a hold of the ConditionName, then I can simply write weather.getConditionName
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and I have to pass in the ID. But wouldn't it be nice if I could just have a property in my weather
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object that's called a condition name and it manages to figure out what that should be.
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Instead of getting my weather manager to call the method getConditionName, in order to get the ID.
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This is a good opportunity to show you a cool thing that we can do in Swift which is called a computed
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property.
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So we've got all three properties here which are actually called stored properties because all they
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do is they just store pieces of data.
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But I can also create a computed property.
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So I'm going to create it using a var keyword and I'm going to call it the conditionName, and it's going
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to have a data type of String, and then I'm going to open up a set of parentheses. And inside the set
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of parentheses, I'm expected to return or output what the value for the condition name should be.
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That would require me to work out the condition name which, luckily, I've already got down here in the
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form of my Switch statement.
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So let's paste that in here and we can use the conditionId property value to switch, and then check
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what condition it is to return this string which is going to be equal to the conditionName.
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So, now I've got a computed property because this property condition name is going to work hard
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its value based on the code inside these curly braces.
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What this allows me to do is if I want to get hold of the weather condition, all I would have to do is
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say weather.conditionName and I can use it just like any other property.
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And if you run your app right now, you'll see it works perfectly
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just like before.
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But our code is now a lot better after the refactoring and it's a lot more succinct and easier to understand.
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So what's a general format for computed properties in Swift?
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Let's go over the syntax for computed properties again. In order to create a computed property,
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it always has to be a var because the value is always going to change. It's going to be based on the
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computation.
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And then we give it a name,
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so let's call it aProperty. And then we have to give it a data type,
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so let's say I want it to be an integer.
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Now, in between the curly braces, I have to provide an output that is going to be set as the value of
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this property.
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So let's say that I wanted to calculate, I don't know, 2 + 5,
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So this is the computation
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and that means aProperty is going to be equal to the result of this computation which is going to be
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7.
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That's all computed property in Swift.
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And as practice and as a challenge, I want you to figure out how we can get hold of the temperature as
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a string with only one decimal place.
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So you've done this before using the string initializer,
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but I want you to turn that into a computed property now, and it should be called temperatureString.
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And if you manage to successfully solve the challenge, then you should be able to print
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weather.temperatureString. And when you run the app and check the weather, then you should get the temperature
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back in a string format with only a single number after the decimal place.
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So pause the video and see if you can complete this challenge.
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All right.
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So we've got a temperatureString computed property here.
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And remember, we always have to provide a data type for the computed property, and then we open a set
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of curly braces and actually work out what it should be.
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So in this case, I'm going to return a String with the format of a single decimal place,
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so thats's "%.1f" and then I'm gonna pass in my temperature which is this Double right
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here as the property that's going to be formatted to this particular format. And now when you run your
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app, you should be able to see that whatever temperature you get back will be printed with only one decimal
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place. And this temperature string now has the data type of a String ready for us to put into our temperature
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label.
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So in the next lesson, we're going to tie it all together and get our weather app working with all of
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these different components together. For all of that and more, I'll see you there.