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Hey guys, welcome to my blog recording my ruby self-taught process
I decided to learn this amazing language while I was trying to solving some ruby challenges to get my tenth badge in HackerRank
At the first two days, We have learned about some common collections such as array and hash in ruby. We have also gotten to know with string.
Today, we will learn more about methods and arguments
str = gets
p str
Output
"hi\n"
I typed hi and hit Enter
As you can see, it also gets the NEWLINE character, which we don’t want to.
So use the chomp method we have learned before to delete that last character at every gets
One more problem here
gets just gets input as raw type, we need to convert it to other type to use it
i = gets.to_i
p i
Output
4
We converted the input to integer, if you type a non-digit character, i will be 0
Convert variable types in Ruby is pretty simple.
# String to integer
i = str.to_i
# String to float
f = str.to_f
# Anything to string
str = ob.to_str
# or if you want to catch error unless user type digit
# String to integer
i = Integer(str)
# String to float
f = Float(str)
def append(*rest)
str = ""
rest.each do |x|
str << x
end
str
end
print append("the", " ", "end")
Output
the end
*rest is a array of all arguments passed
def increase(num1, num2 = 1)
num1 + num2
end
n = 5
puts increase(n)
puts increase(n, 5)
Output
6
10
Convert Temperature program using keyword arguments input_scale and output_scale as default arguments
def celsius_kelvin(num)
return num + 273.15
end
def kelvin_celsius(num)
return num - 273.15
end
def celsius_fahrenheit(num)
return num * 1.8 + 32
end
def fahrenheit_celsius(num)
return (num - 32) / 1.8
end
def kelvin_fahrenheit(num)
return (num - 273.15) * 1.8
end
def fahrenheit_kelvin(num)
return ((num - 32) / 1.8) + 273.15
end
def convert_temp(num, input_scale: 'celsius', output_scale: 'celsius')
return num if input_scale == output_scale
cmd = input_scale << "_" << output_scale << "(#{num})"
return eval cmd
end
puts convert_temp(0, input_scale: 'kelvin', output_scale: 'celsius')
puts convert_temp(393, input_scale: 'kelvin', output_scale: 'celsius')
puts convert_temp(400, input_scale: 'fahrenheit', output_scale: 'celsius')
puts convert_temp(333, input_scale: 'fahrenheit', output_scale: 'kelvin')
Output
-273.15
119.85000000000002
204.44444444444443
440.3722222222222
We could also set a hash parameter ** that helps user pass a key argument
def foo(str: "foo", num: 424242, **options)
options.each_pair do |key, val|
puts key
puts options[key]
end
end
foo(key: "val", key2: "val2")
Output
key
val
key2
val2
Blocks are nameless methods that can be passed to another method as a parameter
def call_block
puts "Start"
yield
puts "End"
end
# Pass a block {puts "I'm in"} to call_block method
# We can pass with do..end
call_block do
puts "I'm in"
end
# or
call_block { puts "I'm in" }
Output
Start
I'm in
End
We can also pass a block to a method that takes parameters
def call_block(a, b)
puts "Start"
yield(a, b)
puts "End"
end
call_block(12, 23) {|a, b| puts a - b}
Output
Start
-11
End
“A Proc object is an encapsulation of a block of code, which can be stored in a local variable, passed to a method or another Proc, and can be called.”
If Block is a nameless method that can be passed to another method right after the method name
Proc is now the object that holding block, we can pass it as a normal variable to another method
def square_of_sum (arr_, proc_sum, proc_square)
sum = proc_sum.call(arr_)
proc_square.call(sum)
end
proc_sum_arr = proc {|arr| arr.sum}
proc_square_number = proc {|x| x**2}
puts square_of_sum([1, 2], proc_sum_arr, proc_square_number)
If Block codes are called by yield key word
Proc codes are called by call() method
Today we have learned how to take user input, convert variables in ruby
We also have learned some advanced ways to create methods and pass arguments
Knowledged a closure object called Proc, and a nameless method called Block
I’d like to thank HackerRank for giving me a chance to acknowledge and be interesting in this cool language
If guys found Ruby is fascinating, please come to the link below and solve some Ruby challenges with me
https://www.hackerrank.com/domains/ruby
If you have any question or suggestion, please let me know at the comment section below.
OK I’m going to wrap this up here
Thanks for reading my blog