String array

With a Ruby string array, we can store many strings together. We often prefer iterators, not loops, to access an array's individual elements.

In Ruby programs, we use string arrays in many places. We can combine and convert string arrays. Ruby supports operators that act upon entire arrays.

Create string arrays

Here we use 2 syntax forms to create string arrays. First, we use the initializer syntax—this requires only one line to create a 3-element array.

# Initialize a three-element string Array.
strings = ["one", "two", "THREE"]
puts strings.length
# Iterate over the strings with "each."
strings.each do |st|
    puts st
end

# Create an array and push three strings to it.
strings2 = Array[]
strings2.push("one")
strings2.push("two")
strings2.push("THREE")
# Write the length and display all the strings again.
# ... Then use a shorter iterator syntax.
puts strings2.length
strings2.each {|st| puts st}
3
one
two
THREE
3
one
two
THREE

Read file lines, chomp

With IO.foreach we efficiently read in the lines of a file, one after another. We use chomp() to remove the trailing newline.

ruby
sapphire
diamond
emerald
topaz
# Create an empty array.
lines = []
# Use foreach iterator to loop over lines in the file.
# ... Add chomped lines.
IO.foreach("/files/gems.txt") do |line|
    lines.push(line.chomp())
end

# Display elements in string array.
lines.each do |v|
    print "[" << v << "]" << "\n"
end
[ruby]
[sapphire]
[diamond]
[emerald]
[topaz]

Combine string arrays

Two arrays can be concatenated with the plus operator. This is an effective way to combine two string arrays.

left = ["virus", "disease"]
right = ["bacteria", "germ"]

# Concatenate the two string arrays together.
# ... The elements are placed together in a four-element array.
result = left + right
puts result
virus
disease
bacteria
germ

2D string array

This example creates a 2D string array and then iterates over it with the each iterator. It displays elements. It accesses a specific element in the top row.

# The first row.
values1 = []
values1.push("AA")
values1.push("BB")
values1.push("CC")

# The second row.
values2 = []
values2.push("DD")
values2.push("EE")
values2.push("FF")

# The 2D array (a container of the other arrays).
container = []
container.push(values1)
container.push(values2)

# Use two iterators to display all strings in 2D array.
container.each do |arr|
    arr.each do |inner|
        print inner << " "
    end
    print "\n"
end

# The 2D array has only two rows.
puts container.length

# Print string cell in middle of top row.
puts container[0][1]
AA BB CC
DD EE FF
2
BB

Split and join strings

These methods involve string arrays. With join, we convert from a string array into a single string with a delimiter in between elements.

items = ["two", "seven", "nine", "forty"]

# Join the string array's elements together.
# ... Display them.
string_value = items.join(",")
puts string_value

# Split apart our newly-joined string.
array_values = string_value.split(",")
p array_values
# We have four string elements.
puts array_values.length
two,seven,nine,forty
["two", "seven", "nine", "forty"]
4

A summary

String arrays are converted into (and from) strings. File handling often involves string arrays. Ruby provides excellent syntax for these common tasks.