zed.0xff.me

Advanced Ruby: percent-literals

most used %-literals:

% code result description
%q %q(all `quotes` 'are' "ok") "all `quotes` 'are' \"ok\"" creates String
%r %r(i_am/a/regexp) /i_am\/a\/regexp/ creates Regexp
%w %w(abc def ghi) ["abc", "def", "ghi"] splits string into Array
%x %x(ls -a /tmp) ".\n..\nfile1\nfile2\n" alias of `cmd`

highlighted

1
2
3
4
5
6
7

%q(all `quotes` 'are' "ok") => "all `quotes` 'are' \"ok\""

%r(i_am/a/regexp)           => /i_am\/a\/regexp/

%w(abc def ghi)             => ["abc", "def", "ghi"]

%x(ls -a /tmp)              => ".\n..\nfile1\nfile2\n"

interpolation

1
2
3
4
5
6
7
8
9
10
11

# lowercase 'w': as-is
%w'a #{2+2} b' => ["a", "\#{2+2}", "b"] 

# uppercase 'W': interpolate
%W'a #{2+2} b' => ["a", "4", "b"] 

# lowercase 'q': as-is
%q'a #{2+2} b' => "a \#{2+2} b" 

# uppercase 'Q': interpolate
%Q'a #{2+2} b' => "a 4 b"

other %-literals

1
2
3
4
5
6
7
8

# %s: convert to symbol
%s'foo' => :foo 

# %i: convert to array of symbols - not released yet, will be in Ruby 2.0 ?
%i'foo bar baz' => [:foo, :bar, :baz]

# '%' w/o any letter - alias for %Q
%'a #{2+2} b' => "a 4 b"

Advanced Ruby: break(value) & next(value)

1. break(value)

break accepts a value that supplies the result of the expression it is “breaking” out of:

1
2
3
4
5

  result = [1, 2, 3].each do |value|
    break value * 2 if value.even?
  end

  p result # prints 4

2. next(value)

next accepts an argument that can be used the result of the current block iteration:

1
2
3
4
5
6
7

  result = [1, 2, 3].map do |value|
    next value if value.even?

    value * 2
  end

  p result # prints [2, 2, 6]