my_name = "Mike Ornellas"
my_name
my_name.downcase
mks_employees = ["harsh", "ravi", "shaan", "shehzan", "matt", "mike", "amanda", "gilbert"]
mks_employees
mks_employees.length
mks_employees.sort
sorted_mks_employees = mks_employees.sort
We can use variables to assign a name to an object. Just like in algebra, the value of a variable can change over time. I can make a variable that is set to a string (like my_name above), or I can store an array in a variable. Heck, we can even store the result of a method in a new variable like we did with sorted_mks_employees up above. In Ruby, we set variables by setting a name equal to something. Unlike strings, these names aren't surrounded by quotation marks - if they were, they would be strings!
name = "Jim"
"name"
name
name = 2
name
Variables are assigned a value with the = method:
empty_array = []
empty_array << "not so empty anymore"
empty_array.push("this is just getting ridiculous")
not_empty_array = empty_array
empty_array.pop
empty_array
not_empty_array
In line 1, we set a variable empty_array to an empty array by setting it to [] and then added items to the end using either the push method or by using the << (shovel) operator to shove something onto the end of the array. Likewise, we can pop things off the end of the array using the pop method which will remove the last item from the array. You can kind of think of pop as taking a chip out of the pringles can, push is putting it back in.
Using variables, we also get another neat tool to use: string interpolation, which is a fancy phrase for something relatively simple.
name = "Mike"
'Hello, my name is ' + name + ', and I am a Ruby developer'
"Hello, my name is #{name}, and I am a Ruby developer"
Both lines should print out the same exact thing, but it's much more common for Rubyists to use the second form with #{} instead. There is one caveat though:
'Hello, my name is #{name}, and I am a Ruby developer'
Not what you expected right? This has to do with the difference between single-quote strings and double-quote strings. Single-quoted strings don't allow for string interpolation, while double-quoted strings do allow interpolation.
We talked about using puts to print strings to the screen, but did you know you could also get input from users? Try user_input = gets.chomp in IRB and then look at the user_input variable to see what is stored. Try doing it without .chomp and see what changes.
In Ruby, you can grab items from an array by their position. So, for example:
color_ary = ["red", "green", "blue", "cyan", "magenta", "yellow", "black"]
color_ary[0]
color_ary[1]
color_ary[2]
color_ary[-1]
Again, this is kind of strange, right? Why do we start at 0 instead of 1? You can think of it like a number line that starts at 0 and goes to 10. The first point on the line would be at 0, the second point at 1, and so on. Arrays work the same way, except we call each point an index, so if we want the first thing in an array, we look at index 0, if we want the second, we look at index 1, and so on.
A crucial aspect of arrays is that you can grab any value from an array based on its position. So, in this example, color_ary[0] grabs the first item in the array (the string "red"), color_ary[1] grabs the second item, and so on. We can also go backwards using negative numbers with the last item being at index -1 and the second-to-last item being at index -2 (like we did above).
We even have some convenient methods to make this a little easier to remember:
color_ary.first
color_ary.last
Can we have both strings and integers in an array? Can you put arrays in arrays? If you can nest arrays like that, how do you access an item in a nested array?
array = [0, 1, 2, [0, 1, 2] ]
array[3]
array[3][0]