Ruby Trick

很喜欢http://www.rubyinside.com这个网站，里面记载了一些Ruby相关的新闻，以及技术相关的，这里爬几个可能会用到的Ruby Trick.

1. 分解枚举

a = %w{a b}
b = %w{c d}
[a + b]                              # => [["a", "b", "c", "d"]]
[*a + b]                             # => ["a", "b", "c", "d"]
a = { :name => "Fred", :age => 93 }
[a]                                  # => [{:name => "Fred", :age =>93}]
[*a]                                 # => [[:name, "Fred"], [:age, 93]]
a = %w{a b c d e f g h}
b = [0, 5, 6]
a.values_at(*b).inspect              # => ["a", "f", "g"]

2. 不用String 或是 Symbol做hash的键

does = is = { true => 'Yes', false => 'No' }
does[10 == 50]                       # => "No"
is[10 > 5]                           # => "Yes"

3.快速赋值

a, b, c, d = 1, 2, 3, 4

def my_method(*args)
  a, b, c, d = args
end

def initialize(args)
  args.keys.each { |name| instance_variable_set "@" + name.to_s, args[name] }
end

4. 使用Range

# if x > 1000 && x < 2000
year = 1972
puts  case year
        when 1970..1979: "Seventies"
        when 1980..1989: "Eighties"
        when 1990..1999: "Nineties"
      end

5. DRY很彻底

%w{rubygems daemons eventmachine}.each { |x| require x }

6. 使用三目运算符(有一天我居然听说一个我的同事工作了六七年，说没用用过这个操作符，天啊，什么世道？什么公司敢用这样的程序员？ 和这样的工作，很危险)

def is_odd(x)
  # Wayyyy too long..
  if x % 2 == 0
    return false
  else
    return true
  end
end

=>

def is_odd(x)
  x % 2 == 0 ? false : true
end

==》

def is_odd(x)
  # Use the logical results provided to you by Ruby already..
  x % 2 != 0
end

7. 写程序要捕捉异常

def do_division_by_zero
   5 / 0
end

begin
  do_division_by_zero
rescue => exception
  puts exception.backtrace
end

8. 确保有东西可迭代

items = "hello"
[*items].each do |item|
  # ...
end

9 捕获异常不一定非要有begin

def x
  begin
    # ...
  rescue
    # ...
  end
end

=>

def x
  # ...
rescue
  # ...
end

10. 块注释

puts "x"
=begin
  this is a block comment
  You can put anything you like here!

  puts "y"
=end
puts "z"

11 rescue to the rescue

h = { :age => 10 }
h[:name].downcase                         # ERROR
h[:name].downcase rescue "No name"        # => "No name"