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Ruby makes heavy use of blocks in the built in types and the standard library. In this video, we explore Strings and Integers.
Documentation Links
Code Samples
String#each_char:
string = "Treehouse"
string.each_char{|c| print "#{c}-"}
This prints out:
"T-r-e-e-h-o-u-s-e"
String#each_line:
haiku = <<-EOF
A string with three lines
Is considered multi line
Ruby code haiku
EOF
haiku.each_line{ |line| puts "* #{line}" }
Prints the following:
* A string with three lines
* Is considered multi line
* Ruby code haiku
Integer#down_to:
5.downto(3) { |number| print number }
Prints out the following:
543
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[SOUND] Ruby makes heavy use of blocks in
0:00
the built in types and
the standard library.
0:04
We've encountered some block methods
before but now that we know more about
0:10
blocks let's take a fresh look at some
of the built in types using workspaces.
0:14
So now that we know more about blocks,
let's go ahead and
0:20
take a look at some of the methods that
take blocks from classes that we've
0:23
seen in the Ruby standard library.
0:28
First, let's go ahead and
take a look at Strings.
0:33
Here is the documentation for
the String class.
0:36
And if we scroll down here on the left,
let's go ahead and
0:40
look at this each_char method.
0:43
Now when we look at the documentation for
something that takes a block, or
0:46
any method really, we can see that it will
show you what arguments the method takes.
0:50
Now when we look at this we can see that
this takes a block with one argument.
0:56
The block is here and
1:02
this arrow means that it returns a String.
1:05
So let's go ahead and open up our
workspace, and I've already launched one.
1:10
I've got it inside of IRB.
1:15
So let's go ahead and take a String
here and we'll just say it's a string.
1:18
And we'll set it to Treehouse, and
1:21
let's go ahead and
practice that each_char method.
1:25
Let's say sting.each_char, and
then we send in the block.
1:27
We know it takes one argument,
we're just gonna call it c, and
1:32
let's print that out,
with a dash right after it.
1:37
So now we can see that this prints out
Treehouse, each character of the String
1:45
and it returns a String itself which
happens to be the original String.
1:51
Now that's useful because we
can do something after that.
1:58
We can kinda chain these
methods if we want to.
2:02
And this doesn't really have anything to
do with the block, it's just kinda cool.
2:04
We could call upcase on that and
then we can see that the actual return is
2:08
TREEHOUSE which is the rightmost
method that's called.
2:12
Now let's go ahead and
look at another method here.
2:17
In addition to each_char,
let's look at each_line.
2:20
This is another method
that takes a block and
2:24
lines are separated by
a new line character.
2:27
So let's go ahead and
test that out in IRB.
2:31
So let's go ahead and
create multi-line String here.
2:33
I'm just gonna call it haiku.
2:36
And we're gonna use the here doc
format to create the String.
2:39
So, here we have our multiline String.
2:55
And then just to demonstrate the each_line
method, we can call each_line.
2:58
And we remember from the documentation,
it takes a block with one argument.
3:04
And let's go ahead and just print that
out with an asterisk in front of it.
3:09
And now we can see our multi-line String
was printed out with an asterisk in front
3:16
of it, just like we expect.
3:20
And then just like the each_char method,
a String is returned.
3:22
So, I'm gonna clear my screen here.
3:29
And then the next method that we're
gonna take a look at is on Integer.
3:30
And this is a neat one.
3:37
We can take any number and
use this downto method, well, any integer.
3:38
And this takes one argument
to the method itself.
3:44
And it takes a block
also with one argument.
3:50
They have an example here in
the documentation, which is 5.downto(1).
3:55
Here's a number, print the number,
and then two dots.
3:59
And that will produce this output.
4:04
Let's go ahead and see if we can
recreate something like that.
4:06
We can say 5.downto(3) and
we'll call that number.
4:10
And let's go ahead and
just print the number.
4:17
That should print out the numbers five,
four, and three right after each other.
4:21
There we go.
And
4:26
then we'll notice here this also returns
the original integer that we send in.
4:27
Now numbers are different, we can't
do something like (5.1).downto(3),
4:33
because the floating point numbers
don't have the downto method.
4:41
And then something else to note
when you're working with blocks,
4:48
it's not necessary to put
all these spaces here,
4:51
that's just the style that I'm
using to make it easier to see.
4:54
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