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Previously, I've challenged you to use the eggTimes dictionary to print out the hardness that was selected
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by the user. To solve this challenge,
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we will combine our knowledge of working with both dictionaries as well as optionals. In order to solve
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this challenge,
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all we had to do was simply, inside our print statement, add the eggTimes dictionary, and then use the
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square brackets to tap into the eggTime that we want depending on the hardness that was chosen by the
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user.
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So in this case, we know that our sender.currentTitle can only be one of three values: Soft, Medium,
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or Hard.
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So if we match these with the keys in our dictionary, then we'd be able to retrieve each of these values.
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So we could simply write eggTimes, and then we could add our hardness in here as the key.
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Now, even though our code seems to work, we get a error from Xcode. And it tells us that "Value of optional
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type 'String?' must be unwrapped to a value of type 'String,'" In order to solve this,
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they give us five ways of fixing it.
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And the reason is because the sender.currentTitle is something that is a bit of a unknown, right?
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You might have a button which triggers this IBAction where it doesn't actually have a title. Well, in
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which case, sender.currentTitle would be equal to nil.
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So then if you have a nil value that you put in here that you try to retrieve from your eggTime dictionary,
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well, then it doesn't know which one to give you, right?
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Nil is not Soft, Medium, or Hard,
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so then we end up with a error
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down the line and our app would crash.
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So to prevent this, the sender.currentTitle has a different data type.
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So you hold down option and you click on it,
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you can see that it's data type is a string question mark which is what we call an optional string.
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So the reason why it's optional is because you could have a button that doesn't, in fact, have 
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a currentTitle,
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so the currentTitle could legitimately not exist. But, of course, in order to use it inside our dictionary
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because all of our dictionary keys are, in fact, pretty solid strings, right?
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They're not optional strings.
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Well, then we have to convert this hardness which comes from sender.currentTitle into a nonoptional.
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One way of doing that, as you might have seen before
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when we use the code from StackOverflow to play sound, we added a exclamation mark at the end of
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sender.currentTitle. So this essentially says that "Yes, I am the human programmer. I know better than you,
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Xcode.
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I know that all three buttons which are linked to my IBAction, so all of the senders will always have
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a current title and this will never fail.
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It'll never crash in the future.
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Don't worry about it."
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So now if we go ahead and run our app, you can see that it actually lets us run the app because errors
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will stop the app from running, but warnings will not.
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So if we now click on each of our buttons, you can see that we get an optional printed.
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I know it seems like we just unwrapped the sender.currentTitle. So why are we seeing an optional again?
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Well, this optional doesn't have anything to do with sender.currentTitle,
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instead, it has something to do with how dictionaries work in Swift.
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Now why is that?
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Why are we getting an optional out of our dictionary?
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Well, our dictionary has keys which are of string data types.
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So let's say that we try to retrieve 5, the value 5 out of our eggTime dictionary.
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Well, I could simply provide the key "Soft," right?
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And when this is printed, we would get 5.
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But what if I had made a typo in this? Because it's a string, right,
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nobody's going to check whether 5 typed it correctly or not.
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Well, in that case, the soft with a lowercase "s" doesn't actually exist in this dictionary as a key.
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So then this result would end up being nil. So if I run this right now and if I press on any of the buttons,
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all I will get is nil because it can't find anything with the key "soft" in this eggTime dictionary.
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So that's why when you provide a key as a piece of text to retrieve an item out of a dictionary, the
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end result will be a optional.
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And I can show you that if I say, let result = eggTimes, and if I hold an option and click on result,
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you can see that the result is actually an optional integer.
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So it's trying to grab an integer out of our dictionary, but it doesn't know if we'll definitely be able
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to find one using this key.
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Then the result becomes an optional.
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So if we wanted to not be an optional, then we could, of course, hit the exclamation mark.
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And in fact, if we were using the hardness value which comes from our button titles, then we know that
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they are for sure spelt correctly because we can see them right here and we can match the spelling of
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the Soft, Medium, Hard with these three keys.
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So in that case, then we can be pretty sure that this result,
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so retrieving an item out of our dictionary is definitely not going to fail ever,
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then we can add an exclamation mark at the end.
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And if we now print our results which has been what we would call unwrapped, then you'll see that instead
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of getting an optional integer, we actually get a actual integer.