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RUBY - STRING

Say if you want to store your name or even a sentence in a variable. How would you do that?

The solution is the String datatype in Ruby.

There are two ways to declare a String :

s = "Robert" or s = 'Robert'

s = String.new("Robert");

Note : String in a mutable class. i.e. Once the values are assigned to a String object,it can be modified or changed.

String Concatenation

Two or more Strings can be concatenated using the + operator or the << operator or the concat method.

If we have two Strings s1 and s2 :

s1 = "Suraj"

s2 = "Singh"

Three ways of concatenating Strings would be :

"The name is " + s1 + s2

"The name is " << s1 << s2

"The name is ".concat(s1).concat(s2)

Example :

s1 = "Suraj"
s2 = "Singh"
puts "The name is " + s1 + s2

Output :

The name is SurajSingh

In the above code we have created two Strings s1 and s2.

s1 = "Suraj"
s2 = "Singh"

And concatenated the String "The name is " with s1 and s2 using +.

puts "The name is " + s1 + s2

Concatenating a String and a Number

Now, let's say you are asked to print the String

Suraj Singh is 29 years old.

The Wrong way :

Let us solve it using the below way :

Example :

s1 = "Suraj"
s2 = "Singh"
age = 29;
puts s1 + " " + s2 + " is " + age +" years old."

Output :

+: no implicit conversion of Fixnum into String (TypeError)
from add.rb:4:in <main>

But the above code will ended up with the above error.

Guess Why?

Let us look at the below line :

puts s1 + " " + s2 + " is " + age +" years old.";

The age variable is holding a number. And in Ruby you cannot concatenate a number and a String using the above code.

The Right way :

It can be corrected by two ways :

Using to_s

to_s is used to convert any other data type to a String. In this case we will be converting an integer to a String.

puts s1 + " " + s2 + " is "+age.to_s+" years old."

Example :

s1 = "Suraj"
s2 = "Singh"
age = 29
puts s1 + " " + s2 + " is "+age.to_s+" years old."

Output :

Suraj Singh is 29 years old.

So, in the above code, we have corrected the problem,

"The 'age' variable is holding a number. And in Ruby you cannot concatenate a number and a String using the above code."

All we have done is, used to_s with age,

age.to_s

And now age is treated as a String.

And when we try concatenating age with the Strings s1 and s2,

puts s1 + " " + s2 + " is "+age.to_s+" years old."

It gives us the right output without any error.

Suraj Singh is 29 years old.

Let us look at the second way to solve the problem.

Using Interpolation - #{}

Interpolation, #{} is just like a placeholder, in which you can place any value irrespective of its data type.

puts "#{s1} #{s2} is #{age} years old."

Example :

s1 = "Suraj"
s2 = "Singh"
age = 29
puts "#{s1} #{s2} is #{age} years old."

Output :

Suraj Singh is 29 years old.

So, in the above code, we have corrected the problem(Well! The second time),

"The 'age' variable is holding a number. And in Ruby you cannot concatenate a number and a String using the above code."

All we have done is, used Interpolation, #{} with the Integer, age and Strings s1 and s2,

"#{s1} #{s2} is #{age} years old."

#{age} is an expression which allows you to insert the number into a String.

#{s1} and #{s2} is just the same as above. i.e. It allows to enter the contents of a String variable within a String.

And when we try concatenating printing the output,

puts "#{s1} #{s2} is #{age} years old."

It gives us the right output without any error.

Suraj Singh is 29 years old.

Now, what if, you want a paragraph, separated by lines, to be assigned to a variable.

i.e. Let's say, you want to assign the below paragraph to a variable.

"We are putting newlines

after every text

and we get the same."

In such cases, you can use double quotes("") or %{}.

Declaring a multiline String with double quotes("") or %{}

Declaring a multiline String with double quotes("") :

Example :

x = "We are putting newlines
after every text 
and we get the same."


puts x

Output :

We are putting newlines
after every text
and we get the same.

Declaring a multiline String with %{} :

Example :

x = %{We are putting newlines
after every text 
and we get the same.
}


puts x

Output :

We are putting newlines
after every text
and we get the same.

Now, if you want to access a particular character of a String, how can you do that?

Say, you have a String "Hello". And you want the letter e to be assigned to a variable.

Let us see below.

Accessing the characters of a String

Example :

x = "Hello"
y = x[1]
puts y

Output :

So, we have a string Hello,

x = "Hello"

And we have assigned Hello to a variable x.

Let us elaborate more, on how the String Hello is stored in the variable x.

So, just for the sake of understanding, you can assume the variable x is divided into 5 parts to store Hello.

Now, if you check from the front, the count starts from 0 and ends with 4.

Similarly, if you look from the reverse direction, the count starts from -1 and ends with -5.

So, if we look at the next line in the code,

y = x[1]

We are trying to access the 2nd location,

So, x[1] is referring to the 2nd location where e is stored.

y = x[1]

And we have assigned e to the variable y.

Note : The square brackets '[]' are used with the string type variable to get the variable at that position(i.e. x[1] refers to the 2nd location that contains 'e').

Now, if you look at the print statement,

puts y

The value of y is printed as output.

Output :

Also, remember that x[1] and x[-4] is referring to the same location that has e. You can use the negative positions or positive. That is completely upto you.

Example :

x = "Hello"
y = x[-4]
puts y

Output :

Next, let us see, how can we access a portion of a String. i.e. Say you want to take ell from the String Hello and store it in a different variable.

Accessing a chunk of letters/characters from a String

Example :

x = "Hello"
y = x[1,3]
puts y

Output :

ell

So, we want to take the chunk of letters/characters from the String Hello and store it into the variable y.

And in the first line, we have stored Hello inside x.

x = "Hello"

Also, let us see the elaborated structure.

So, we want to take the chunk ell from Hello. And that happens in the next line.

y = x[1,3]

Just note, the position of e from ell is 1 and the position of the last l from ell is 3.

So, the statement x[1,3] simply refers, "Pick the chunk from index 1 to index 3".

And ell is assigned to the variable y.

And in the next line, we have the print statement,

puts y

That prints the chunk of letters ell.

Output :

ell

String Replication

String Replication is a cool feature provided by Ruby. Say you want to print the name Robert 5 times.

The below code does it for you :

puts "Robert " * 5;

Output :

Robert Robert Robert Robert Robert

Getting the length of a String

Example :

s = "Robert";
puts s.length;

Output :

Getting a chunk of String

Say we want to get "ber" from the String "Robert".

Example :

s = "Robert";
puts s[2,3];

Output :

ber

In s[2,3] the first number 2 is the index(index starts from 0), which is b. And the number 3 is the length of the String to be fetched.

So if you wanted to fetch bert. It would have been

puts s[2,4];

String Comparison

The == operator

Returns true if the condition matches else returns false.

Example :
```
s = "Robert"
puts s == "Robert"
```
Output :

true

The eql? Operator

Returns true if the condition matches else returns false.

Example :
```
s = "Robert"
puts s.eql?"Robert"
```
Output :

true

The casecmp method

Returns three values, -1, 0 and 1. If the condition matches, it returns 0. And returns 1 and -1 if the values don't match.

Let us see them with the below example.

Example :
```
s = "Robert"
puts s.casecmp "Robert"
```
Output :

0

Now, since the condition matched, it returns 0.

Let us see the next example.

Example :
```
s = "Robert"
puts s.casecmp "Robera"
```
Output :

1

Now, there is a mismatch, as we are trying to compare the String Robert
```
s = "Robert"
```
With Robera,
```
puts s.casecmp "Robera"
```
Now, since the values didn't match, it returned 1.

But why not -1?

Just note, there is just a mismatch of one letter i.e. The last letter of Robert is t and the last letter of Robera is a.

Now, since a is less than t. It returns the value 1 in case of mismatch.

Similarly, the below example also returns the value 1,

Example :
```
s = "Robert"
puts s.casecmp "Rober"
```
Output :

1

Because there are less letters in Rober.

In the same way, the below example,

Example :
```
s = "Robert"
puts s.casecmp "Roberz"
```
Output :

-1

Now, there is a mismatch, as we are trying to compare the String Robert
```
s = "Robert"
```
With Roberz,
```
puts s.casecmp "Robera"
```
Now, since the values didn't match, it returned -1.

But why not 1?

Just note, there is just a mismatch of one letter i.e. The last letter of Robert is t and the last letter of Robera is z.

Now, since z is greater than t. It returns the value -1 in case of mismatch.

Similarly, the below example also returns the value -1,

Example :
```
s = "Robert"
puts s.casecmp "Robertv"
```
Output :

-1

Because there are more letters in Robertv.

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RUBY - STRING

String Concatenation

Example :

Output :

Concatenating a String and a Number

The Wrong way :

Example :

Output :

The Right way :

Using to_s

Example :

Output :

Using Interpolation - #{}

Example :

Output :

Declaring a multiline String with double quotes("") or %{}

Example :

Output :

Example :

Output :

Accessing the characters of a String

Example :

Output :

Output :

Example :

Output :

Accessing a chunk of letters/characters from a String

Example :

Output :

Output :

String Replication

Output :

Getting the length of a String

Example :

Output :

Getting a chunk of String

Example :

Output :

String Comparison

The == operator

Example :

Output :

The eql? Operator

Example :

Output :

The casecmp method

Example :

Output :

Example :

Output :

Example :

Output :

Example :

Output :

Example :

Output :