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Closures

2:36 with andi mitre

In Scala you can define a function inside another function or method and then access any variables in the enclosing scope. In this video we’ll learn about closures and how to implement them.

New Terms:

Closures -- A closure is a function whose return value depends upon a variable declared outside the function scope

Further Reading:

Examples of closures
Scala style Next steps with Scala

  • 0:00

    A closure is a function whose return value depends upon a variable

  • 0:04

    declared out the function scope.

  • 0:07

    Basically with closures, means a variable and

  • 0:10

    a function where the variable is no longer in scope.

  • 0:13

    Let's dive in and create a closure.

  • 0:16

    Let's create a function called a reverse it which will take a string argument

  • 0:20

    consisting of our superhero name and a prefix.

  • 0:23

    Then it will concatenate the two and reverse the result.

  • 0:27

    Let's dive back into the code editor and clean up some of our earlier code.

  • 0:56

    So far, we've created a prefix variable which is not a vowel because we'll need to

  • 1:01

    change this later in the reverse hit function.

  • 1:05

    Let's see how we can use these two, to really show how powerful closures can be.

  • 1:17

    In this case, we call the function reverse it by passing the value Thor.

  • 1:22

    Let's also check out another example.

  • 1:25

    Let's change prefix to "Super Fast."

  • 1:41

    In the second example, we call reverseIt, passing it "Wonder Woman." And

  • 1:45

    also we've changed the prefix to super fast.

  • 1:49

    But what happens when we print out Thor and or when we print out Wonder Woman?

  • 1:59

    Let's compile and check out the results.

  • 2:04

    Although it's a bit difficult to read,

  • 2:06

    we notice that that first prefix is set to lightning.

  • 2:10

    And the reverse it function uses the variable prefix which is not in scope.

  • 2:15

    We update the variable prefix to super fast.

  • 2:18

    However, calling Thor retains the correct instance of prefix.

  • 2:23

    I hope you enjoyed exploring Scala with me.

  • 2:26

    We've gone through quite a few concepts through out the stages.

  • 2:29

    And learned quite a bit about Scala.

  • 2:31

    Checkout the teachers notes for more resources and how to proceed from here.

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