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Hello.
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The first interview question we'll talk about is "What is the difference between tuples and ValueTuples?"
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First, let's make sure we understand what tuples are on the conceptual level. Tuples are small data
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structures used to bundle a couple of pieces of information together.
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This can be useful when, for example, I wanted to create a method that needs to return two pieces of
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information without declaring a dedicated type for it.
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Let's create a simple tuple holding an int and a string.
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I could also create a tuple using the Tuple.Create method, which is more convenient as it doesn't require
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providing the type parameters. It confers them from provided values.
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I can access the values held in the tuple using the Item1 and Item2 properties.
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Please be aware that we can hold more than two elements in a tuple.
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The maximum is eight.
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So calling the Create method or the constructor with more than eight parameters will not compile.
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There is a way of bypassing this limitation by simply making the tuple nested. We can just declare
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a tuple of tuples.
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In C@ we have two kinds of tuples:
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Regular tuples and ValueTuples.
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Before we move on, let me clarify one thing.
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From now on, when I will be using the word "tuple", I will be meaning the System.Tuple type. When I will have
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ValueTuple in mind
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I will use its full name.
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All right.
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Let's see some ValueTuples. On the conceptual level
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they serve the same purpose as tuples, so they bundle a couple of values together.
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I could create a ValueTuple
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with a constructor call.
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But for ValueTuples, there is a much simpler way to create them.
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As you can see, the construction of a ValueTuple looks much nicer than the creation of a tuple.
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Let's discuss other differences between tuples and ValueTuples.
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First of all, tuple is a reference type, while ValueTuple is a value type.
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This has a lot of implications.
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For example, tuples are compared by reference while ValueTuples are compared by value.
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We can compare tuples by value if we need to, buy using the Equals method, which tuple overrides.
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Let's see some code that compares tuples and ValueTuples.
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All right, those two tuples and those two ValueTuples are equal by value.
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Let's see what will be presented to the console.
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As you can see, the euqlity operator gives false for tuples because as reference types, they are compared
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by reference. The fact that tuples are reference types can have negative performance implications.
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Couples are usually short-lived objects, and if we create a lot of them, the process of allocating
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and freeing the memory might take considerable time.
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This was one of the reasons why ValueTuples were introduced
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with C# 7. The next difference that we must be aware of is that tuples are immutable and ValueTuples
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are mutable.
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If an object is immutable, it means it cannot be modified once it has been created.
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We'll learn more about immutable types later in the course.
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As you can see, modifying the item of a tuple doesn't work, but it works fine for ValueTuples.
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The difference that probably matters most for us as the developers, is that for ValueTuples we can
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give names to the fields that they contain
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and we don't need to use those awkward Item1 and Item2 nams.
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However, we still can if we want to.
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As you can see, this looks much better than this.
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The last difference is that we can create ValueTuples with more than eight elements.
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In the document attached to this lecture, you can read in detail how it works under the hood.
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All right, let's summarize the differences between tuples and the ValueTuples. Tuples are reference
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types, ValueTuples are value types. When a lot of short-lived tuples are created
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it may decrease the performance of the application as the memory management for reference types is more
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demanding than for value types.
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ValueTuples provide a convenient syntax for creation. In tuples
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all properties are named Item1, Item2, and so on.
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The fields of the ValueTuples can have names.
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Tuples are immutable.
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ValueTuples are mutable.
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ValueTuples can easily be declared with more than eight elements.
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When discussing tuples during the interview, you can be asked the following question: "Is it possible
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to have a tuple with more than eight elements?"
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Well, tuples are limited to hold up to eight elements, and the only way to bypass this limitation
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is to make the tuple nested.
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So, for example, we can have a yuple of eight elements in which the last one is also a yuple of eight
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elements. For ValueTuples
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we can easily declare them with more than eight elements.
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All right, that's it for this lecture.
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Thanks for watching, and I'll see you in the next one.