each-Select

While Ruby’s 

each

 method is useful, it also comes with an awesome extended family of methods that are even more powerful!

For the next few examples, we’ll work with a slightly more complex data structure. It look like this:

friends = [
{
name: "Diego",
status: "Online"
},
{
name: "Liam",
status: "Away"
},
{
name: "Gloria",
status: "Online"
},
{
name: "Charlie",
status: "Away"
}
]

select

 is similar to 

each

 in that we pass it a block to run on each element in the collection, but the similarities stop there. The important difference is that 

select

 will return a new collection with only the items that
the block returned 

true

 for. It sounds pretty intimidating at first, so let’s walk through an example.

We can use 

select

 to create a new Array filled with only our online friends:

online_friends = friends.select do |friend|
friend[:status] == "Online"
end

Because the block is so short, it would also work well as a one-liner:

online_friends = friends.select{|friend| friend[:status] == "Online"}

select

 will go through each element one at a time, starting with 

{name: “Diego”, status: “Online”}

, passing it to the block we wrote. The block contains a single line: 

friend[:status] == “Online”

.
That line returns either 

true

 or 

false

. If the block returns 

true

, that specific item is added to a new Array that will be returned at the very end of 

select

.
This table shows each step of the process:

 



 

At the very end, 

select

 returns this Array which we save to a new 

online_friends

 variable:

[{ name: "Diego", status: "Online"}, { name: "Gloria", status: "Online"}]