- Blocks in the Wild: Strings and Integers 4:58
- Block Method Practice: Strings 1 objective
- Blocks in the Wild: Arrays and Hashes 7:06
- Block Method Practice: Arrays 1 objective
- Build a Simple Benchmarker 6:31
- Block Method Practice: Custom Classes 2 objectives
- Implementing Block Methods 3:30
- Implementing Block Methods 1 objective
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Implementing Block Methods
3:30Blocks are easy to use in our classes. In this video, we'll practice writing a class that mimics arrays.
Now that we know how blocks work.
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Let's practice a little bit more by
re-implementing some methods that we've
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already seen.
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Okay.
So the next thing that we're gonna do
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is take a look at a built in
method by re-implementing it.
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And what we're gonna do
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is create a new class that
functions kind of like an array.
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We're gonna call it my_array.rb.
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So this is going to need to be a class,
MyArray.
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So we'll define the class,
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and we'll have the initialize method,
and for
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right now we're going to
use the built in array.
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Let's go ahead make that attr_reader,
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so that we don't have to use the at
sign each time we wanna access it.
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And so we'll make a push method, so
that we can append items to this array.
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We're not doing anything crazy with it.
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But what we really want to do is
see how the each method works,
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so let's implement our own.
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And we can do that by
writing the each method.
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We'll say the each method takes a block.
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So now, what do we do?
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Well, in an array, the each method
iterates over each item in the array,
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and we pass a block to that method.
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So, we could say that the block is
called on each item in the array.
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So, let's go ahead and iterate over each
item, and we'll use a while loop for this.
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We'll say i is zero for our iterator.
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And while i is less
than the array's length,
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we have a block there,
and we return the array.
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So what goes inside this block?
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Well, we'll call the block
that is passed in
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on the current item in the array.
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Now, we could run this right now, but
this is currently an infinite loop.
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What we have to do is increment
our iterator variable.
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So now, let's go ahead and
create a new array.
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And we'll add some items to it.
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And now we can go ahead and
write our block.
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My array.each|item|,
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we'll just say, puts "item".
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Now I'm going to save that and
run this by typing ruby my_array.rb.
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Oh, oh.
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Undefined local variable or
method i for main object.
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And that's on line 14 called from line 26.
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And the problem here is that on line 26,
I tried to call i
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instead of item,
item is what I'm passing in to the block.
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So that would be the issue.
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Let's clear the screen,
and run this again.
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And we can see that this block is
executed for each item on my_array.
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Great job, everybody.
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