Getting user input
Let's make the program that greets the user. We will ask the user
for his or her name, and then say 'hello'. We use the gets
method to get the user input (as a string).
Save this and run it:
What happened? Why did it go to the next line?
It went to the next line because you typed a new-line
character. That is, because you pressed Enter.
This will make more sense if we bo back to irb. Start
irb and type the gets line. When the computer waits
for the input type in a name. Look carefully at what happens:
What's that "\n" at the end of the string?
That "\n" represents a new-line
character. This is the character that your keyboard sends when you
press the Enter key.
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Tip:
See how we used irb to figure out what was happening?
Whenever something doesn't go the way you expect, it is a good idea
to try it out in irb.
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Okay, we know what's wrong. But how do we get rid of that pesky
new-line?
Ruby strings come with the method String#chomp for
precisely this purpose. Let's go back to irb so we can see
it in action.
Beautiful! The String#chomp method gives you back the
string, but without the terminating newline. So now we can write:
Notice that name still contains the new-line. It's
chomped_name we want. But why have another variable?
It's better to just write:
>> name = name.chomp
Now name has the new-line removed.
Now we can go back to our program and fix the problem.
Now, here is a neat thing about Ruby:
- chomp is a string method (String#chomp).
- gets returns (gives you back) a string.
Therefore, you can write gets.chomp to make String#chomp
be called on whatever gets returns. In other words, we can write:
Now, isn't that beautiful?
Type this in and run it:
Write a program that will take two words and print them in
opposite order.
Write a program that behaves like this:
Assume that the year the user was born is simply the
current year minus the age. Remember String#to_i
Write a program that asks for a number and a sentence
and prints the sentence backwards that many times. It should:
There is more than one way to make this program. Use any you
like.
What do you think this line does?:
number = gets.chomp.to_i
Try it out in irb.
Write a factorial program, which takes a number from the
user and computes the factorial. It should behave similar
to this:
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