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Ruby Blocks

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Build a Monster Class: Part 4

2:49 with Jason Seifer

In this stage, we'll be working towards creating our own class that uses blocks, arrays, hashes, and more. In this video, we'll learn a neat trick about yielding to blocks.

Code Samples

The following code will return the current object in context to a block:

yield self if block_given?

This is useful in cases where you would like to have access to the class inside of a block.

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    So we're done with our Monster program, 0:00
    but I wanted to show you something really cool that you can do with blocks. 0:02
    So, here we have our different actions and 0:07
    we're calling them within the context of a block. 0:13
    Let's just see what the last thing that we have here, okay, monster.hide. 0:16
    Let's go to this hide method, and we yield to the block, 0:20
    which means we're coming out of this method, and calling that block. 0:25
    So, it jumps from here, in this hide method, 0:30
    down to monster.hide, right here, and executes this block of code. 0:34
    Something that's kind of neat that we can do is yield arguments to the block. 0:42
    Now we know that from earlier lessons that we can provide arguments to the block. 0:48
    So, we'll just say if a block is given here, 0:54
    let's provide this argument and what argument would that be? 0:59
    Well, if wanted to we could provide the actions variable and 1:04
    then we would have access to that in the block, but 1:08
    let's do something a little more interesting and yield self. 1:12
    self is the instance of the monster. 1:18
    So we'll get the monster instance inside of the block. 1:23
    Which means, 1:26
    we could put this in as an argument called monster. 1:33
    And in here, we would have access to the monster variable. 1:38
    And actually, let's just put that in as m. 1:43
    And let's print out the actions here, just to see what it looks like. 1:47
    Printed out the scoreboard. 1:58
    Let's go back up. 1:59
    And this is pretty neat right here, screams, scares, runs, and hides. 2:01
    And let's go ahead and just prove that we can get access to all the methods in here. 2:07
    We define an inspect method. 2:13
    We'll just say inspect is the name and the actions. 2:19
    Clear my screen. 2:32
    Run this one more time. 2:33
    And here we go, 2:36
    we've implemented an inspect method that we call from inside of this block. 2:37
    This is not something you totally need to do, but it is pretty cool and 2:43
    something that you will see in Ruby programs. 2:46

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