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In this section, we're going to take a look at references and borrowing references allow us to make

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a reference to a value without taking ownership of it.

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Okay.

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We're borrowing the value.

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We have two types of references shared and mutable.

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A shared reference is going to let you read but not modify whatever is being referenced to.

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You can have as many shared references to a particular value at a time as you desire.

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Mutable references, on the other hand, allow you to both read and modify the value.

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However, unlike a shared reference, you cannot have any other references of any sort to that value

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active at the same time.

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So let's take a look at this.

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So we'll start out by saying let's equal string from hello.

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And then we want to create a function called change string and we want to take in some string of a reference

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to a string.

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And then we want to take some string and.

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Push something onto it.

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So here we want to say change a reference and then to s so we make a reference.

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I.

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Using the ampersand sign so we can see we're already getting an error here and it's telling us, Hey,

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we need to make some string mutable.

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So the first thing we need to do is say Let s be mutable.

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And then here we need to make.

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It's known that it's going to be a mutable reference.

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And then down in here, we've got to do the same as well.

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So now all of our compiler errors are are gone.

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So let's see.

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What happens when we print it out.

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And so we're expecting SSE to come back and say Hello World, which is exactly what happens.

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And we were able to do this because we added the mute keyword, so making it mutable to the variable

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and inside the function argument.

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So after running cargo run, we were able to see that we change the variable without ever taking ownership

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of the variable inside the function.

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Because if we didn't pass it by reference, then change string would have taken ownership of S.

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Therefore, S would not have been able to have been used here.

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So that is the power of references and borrowing and rust and it's a concept that we are going to use

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throughout the remainder of this course.

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So it's very important to understand this.

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The next section, we're going to start taking a look at Starbucks and Lifetime's and continue building

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upon this idea of ownership, referencing and borrowing.