Better In Ruby - 02
Some tips you probably don’t know in Ruby - 02
In this article, I want to show you some nice Ruby features that you may know or not. Anyway, it’s a quick read and it’s always interesting to learn new stuff, right?!
Create a hash from a list of values
You can create a hash from a list of values by using Hash[…]. It will create a hash like below:
Hash[, , , ]
# => {"key1"=>"value1", "key2"=>"value2"}
Lambda Literal ->
Lambda Literal is a anonymous function like lambda in python, => in JS or C#, allows you to create lambda easily.
a = -> { 1 + 1 }
a.call
# => 2
a = -> (v) { v + 1 }
a.call(2)
# => 3
Double star (**)
The double star is a neat little trick in Ruby. See the following method:
return a, b, c
end
a is a regular parameter. *b will take all the parameters passed after the first one and put them in an array. **c will take any parameter given in the format key: value at the end of the method call.
See the following examples:
One parameter
my_method(1)
# => [1, [], {}]
More than one parameter
my_method(1, 2, 3, 4)
# => [1, [2, 3, 4], {}]
More than one parameter + hash-style parameters
my_method(1, 2, 3, 4, a: 1, b: 2)
# => [1, [2, 3, 4], {:a=>1, :b=>2}]
Handle single object and array in the same way
Sometimes you might want to give the option to either accept a single object or an array of objects. Instead of checking for the type of object you’ve received, you could use [*something] or Array(something).
Let’s assign two variables. The first one is a single digit and the second one is an array of digits.
stuff = 1
stuff_arr = [1, 2, 3]
In the following example, I use [*...] to loop through whatever is give
[*stuff].each { s }
[*stuff_arr].each { s }
Same in this one but using Array(…).
Array(stuff).each { s }
Array(stuff_arr).each { s }
Double Pipe Equals ||=
The Double Pipe Equals is a great tool to write concise code.
It’s actually equivalent to the following:
a || a = b # Correct
And not this one, as a lot of people think:
a = a || b # Wrong
The second one doesn’t make sense because there is no point reassigning a if we already have it!
This operator can be used to create methods like this in your classes. I love to use it for calculations.
@total ||= (1..100000000).to_a.inject(:+)
end
Now you could have other method calling total to get the total value but it will only be calculated the first time.
Mandatory hash parameters
This one was introduced in Ruby 2.0. Instead of just defining a method that takes a hash in parameters like this:
end
You can specify the keys that you are waiting for and even define default values for them! a and b are mandatory keys.
return a, b, c
end
We can try to call it without giving a value for b but it won’t work.
my_method(a: 1)
# => ArgumentError: missing keyword: b
Since c has a default value, we can just call the method with a and b.
my_method(a: 1, b: 2)
# => [1, 2, "default"]
Or with all of them.
my_method(a: 1, b: 2, c: 3)
# => [1, 2, 3]
All we are doing is passing a hash and using some visual shortcuts but obviously, you can also pass a hash like this:
hash = { a: 1, b: 2, c: 3 }
my_method(hash)
# => [1, 2, 3]
Generate array of alphabet or numbers
You might want to generate a list of numbers or put the entire alphabet inside an array. Well, you can use ruby ranges to do this.
A to Z
(..).to_a
# => ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"]
1 to 10
(1..10).to_a
# => [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
Tap
Tap is a nice little method that improves code readability. Let’s take the following class as an example.
attr_accessor :a, :b, :c
end
Now let’s say you want to instantiate a new user and assign a value to each of its attributes. You could do it like this:
o = User.new
o.a = 1
o.b = 2
o.c = 3
o
end
Or you could use tap to do it like this.
User.new.tap do
o.a = 1
o.b = 2
o.c = 3
end
end
Basically, the tap method yields the calling object to the block and returns it.
Thanks you for reading! Stay tunned to update the next chapter.