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Hey, guys.
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Welcome to another Swift Deep Dive. In this lesson, we're going to cover
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Swift Dictionaries, just like the array collection type. Dictionaries are another collection data type
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in Swift.
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So how do they work?
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Well, just as how if you'll look inside a dictionary, you'll find words and each word has an accompanying
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explanation or meaning.
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Well, in programming, we have a similar concept. So you could express this dictionary entry in code like
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this. So you could create a dictionary variable and set it to equal a collection, so all collections in
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Swift start and end with the square brackets. And as opposed to an array where we just have a whole bunch
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of items separated by commas, in a dictionary, we have what's called a key-value pair where the key is
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simply the item that we could look up, say, the words in a dictionary, and the value is the accompanying
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piece.
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So in this case, it's the definition of this word.
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Now, you're not limited to just a single entry per dictionary.
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You can have as many as you want.
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So for example, we can have a dictionary where we have a brewery and the definition of a brewery, and
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then we could have a bakery
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and the definition of a bakery.
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So we have multiple key-value pairs which are separated by the comma.
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Now, in this case, in my dictionary, my key and my value have the same data type that both strings, the pieces
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of text, but you can mix it up. You can have a dictionary where you have a string as the key and an integer
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as the value.
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For example, you could create a phonebook dictionary where you had each of your friends names and their
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phone numbers stored in separate key value pairs.
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And notice how in this case, I'm actually specifying an explicit data type, instead of using type inference.
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So when I create my dictionary, I specify a data type using the colon, and then I say that this is going
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to be a collection type,
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so square brackets and the key.
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So the first item is going to be of string data type, and then the second item, the value is going to
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be of integer data type.
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So now I can stuff as many of these key-value pairs into my dictionary as I want as long as I stick
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to those data types.
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So keys being strings and values being integers.
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If we think about arrays and we think about the way that we create an array, we simply stuffed a whole
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bunch of value separated by commas into a collection, right, into a set of square brackets. And then when
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we had to retrieve an item from the array, we use the name of the array, and then we added a set of square
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brackets at the end and we put in an index value,
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so a number that pointed to the item that we wanted from the array.
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So in this case, this particular line of code would actually retrieve the word "brewery."
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Now, how does it work for dictionaries?
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Well, in this case, our dictionary would be defined like so.
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So it's a string int dictionary.
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And when we want to retrieve a item out of our dictionary, we instead of adding a number, we use the key.
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So we would use the name of the dictionary which is called dict and then we add a set of square brackets
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just as we did for arrays. But now we provide the key that we want in order to retrieve the value which,
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in this case, this line of code would be equal to 07712345678.
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So now that you've learned about dictionaries, complete the Dictionary assignment.