Include

Does an array or string contain a specific value? With Ruby we can use a loop or an iterator to search. But another approach can be used.

With include, we can search an array for a value in a single method call. This is easier to read and easy to use. We must include a question mark at the end of include.

Array example

Let us begin. This program uses an array of 3 integers. It then searches the array with "include" 2 times. The first tested value, 200, is found.

And The include method returns true if a value if found. If a value is not found, it returns false.

Next The program searches the "values" array for 999, which is not found. It prints a helpful message.

values = [10, 200, 3000]

# See if array includes this value.
if values.include?(200)
    puts "ARRAY CONTAINS 200"
end

# See if array does not include this value.
if !values.include?(999)
    puts "ARRAY DOES NOT CONTAIN 999"
endARRAY CONTAINS 200
ARRAY DOES NOT CONTAIN 999

`String` include

Is one string contained within another? The "include?" method in Ruby tells us. It searches one string for a second string. It returns true or false.

Here We see that the string "plato" contains the string "to". It does not contain the string "not".

And The "include?" method is case-sensitive. This means the string "plato" does not include the string "PLA".

value = "plato"

# String includes "to".
if value.include? "to"
    puts "1"
end

# String does not include "not".
if !value.include? "not"
    puts "2"
end

# String does not include "PLA" uppercase.
if !value.include? "PLA"
    puts "3"
end1
2
3

Some notes

In Ruby, a method that ends in a question mark is a predicate method, one that returns true or false. With "include we get a boolean result.

A summary

Methods that use iterators usually will involve more code than "include." But they also may be more powerful—you can add more steps to the iterator than you can to "include."