Ruby from zero to hero

This is your life. Do what you love, and do it often.

Run ruby in 1 second

Just type irb (Interactive Ruby) in your terminal, you’ll get get a Ruby interactive environment, so just type “hello world”, you’ll see the result directly.

Or just run “puts todd” it will output it to console.

Call functions in primitive variable

One difference to Java, you can invoke function on primitive variables, e.g. call method times on int as below

3.times do
  print 'Welcome '
end

Call a function directly, no need parenthesis

In other language, such as Java, you have to suffix () even there is no any arguments. However in Ruby, it’s save your time for such boilerplate

"todd".reverse
"todd".length
"todd"*5

To call a function of String on integeger won’t work, so suffix to_s after number and try

168.to_s.reverse

Similarly, you can call to_i to convert to integer and to_a convert to array

Functions on list

[12,52,26].max

! is another syntax sugar

Please see the big exclamation at end of a method ticket.sort!, this means the call method will alter the variable for good. On the other hand, no ! means leave original variable NOT changed

ticket=[15,6,98,55]
puts ticket
puts "======"
ticket.sort!
puts ticket

Methods chain

You can join multiple methods calls in a chain

puts poem.lines.reverse.join

hash map in Ruby

books={}
books["Gravitys Rainbow"]=:splendid

Did you realized the : in front of splendid? This is actually indicate it’s a symbol

When you place a colon in front of a simple word, you get a symbol. Symbols are cheaper than strings (in terms of computer memory.) If you use a word over and over in your program, use a symbol. Rather than having thousands of copies of that word in memory, the computer will store the symbol only once.

To loop hash map values

ratings = Hash.new{0}
books.values.each{ |rate|
  ratings[rate]+=1
  }
puts ratings

To loop a fixed times by assigning a primitive number

Different to Java or other language, you can call method on top of a int value directly, then apply functions in a block .

Moreover, you can surround input variable for the block with two pipes symbol.

5.times {print "*===="}
5.times { |time|
  puts time
}

parenthesis is optional and better to not

with or without parentheses is the same to Ruby, but the version without parentheses is a bit easier to read. And it saves you valuable typing time!

puts "Hello"
puts("Hello")


def tame(number_of_shrews)
  number_of_shrews.times {
    puts "tamed a shrew"
    }
end

tame(5)

To convert JSON to hashmap easily

s = get_shakey
s["William Shakespeare"].each { |key,val|
  puts val["title"]
  }

High end functions in hashmap

You can call select to filter hashmap then use count to gather number of occupance

def count_plays(year)
  s = get_shakey

  s["William Shakespeare"]
    .select { |k, v|
      v["finished"] == year
    }.each { |key, val|
      puts val["title"]
    }.count
end

puts count_plays(0)

–End–