船長日誌

De?ning a Method
Method names should begin with a lowercase letter.
Methods that act as queries are often named with a trailing ?,
Methods that are “dangerous,” or modify the receiver, may be named with a trailing !.
methods that can be assigned to end with an equals sign (=).

def cool_dude(arg1="Miles", arg2="Coltrane", arg3="Roach")
  "#{arg1}, #{arg2}, #{arg3}."
end

def my_other_new_method
  # Code for the method would go here
end

Variable-Length Argument Lists(*, asterisk ->Array)
def varargs(arg1, *rest)
  "Got #{arg1} and #{rest.join(', ')}"
end
varargs("one")                      "Got one and "
varargs("one", "two")    "Got one and two"
varargs "one", "two", "three"       "Got one and two, three"

Methods and Blocks
def take_block(p1)
  if block_given?
    yield(p1)
  else
    p1
  end
end
take_block("no block")                           "no block"
take_block("no block") {|s| s.sub(/no /, '') }   "block"

if the last parameter in a method de?nition is pre?xed with an ampersand(&),any associated block is converted to a Proc object, and that object is assigned to the parameter.

class TaxCalculator
  def initialize(name, &block)
    @name, @block = name, block
  end
  def get_tax(amount)
    "#@name on #{amount} = #{ @block.call(amount) }"
  end
end
tc = TaxCalculator.new("Sales tax") {|amt| amt * 0.075 }
tc.get_tax(100)       "Sales tax on 100 = 7.5"
tc.get_tax(250)       "Sales tax on 250 = 18.75"

Calling a Method

Method Return values
def meth_three
 100.times do |num|
   square = num*num
   return num, square if square > 1000
 end
end
meth_three → [32, 1024]
num, square = meth_three
num      → 32
square   → 1024

Expanding Arrays in Method Calls
def five(a, b, c, d, e)
  "I was passed #{a} #{b} #{c} #{d} #{e}"
end
five(1, 2, 3, 4, 5 )            "I was passed 1 2 3 4 5"
five(1, 2, 3, *['a', 'b'])       "I was passed 1 2 3 a b"
five(*(10..14).to_a)             "I was passed 10 11 12 13 14"

Making Blocks More Dynamic
    print "(t)imes or (p)lus: "
    times = gets
    print "number: "
    number = Integer(gets)
    if times =~ /^t/
      calc = lambda {|n| n*number }
    else
      calc = lambda {|n| n+number }
    end
    puts((1..10).collect(&calc).join(", "))
produces:
    (t)imes or (p)lus: t
    number: 2
    2, 4, 6, 8, 10, 12, 14, 16, 18, 20

Collecting Hash Arguments
class SongList
  def create_search(name, params)
    # …
  end
end

list.create_search('short jazz songs',
                   :genre              => :jazz,
                   :duration_less_than => 270)