stupid ruby tricks

and some useful ones

Nick Quaranto @qrush

`ruby -c`: Syntax checking

$ echo "class Foo" | ruby -c
  -:1: syntax error, unexpected $end

$ echo "class Foo; end" | ruby -c
  Syntax OK

`ruby -w`: Indent checking (1.9+)

$ cat bad.rb
class Foo
  def bar
    if false
      puts "LOL"
  end
end

$ ruby -w bad.rb
bad.rb:5: warning: mismatched indentations at 'end' with 'if' at 3
bad.rb:6: warning: mismatched indentations at 'end' with 'def' at 2
bad.rb:6: syntax error, unexpected $end, expecting keyword_end

`ruby -p, -e, -i`

$ echo matz | ruby -p -e '$_.tr! "a-z", "A-Z"'
MATZ
$ echo matz > /tmp/junk
$ cat /tmp/junk
matz
$ ruby -p -i.bak -e '$_.upcase!' /tmp/junk
$ cat /tmp/junk
MATZ
$ cat /tmp/junk.bak
matz

underscores in numbers

1_000.times do
  puts "ROFL!"
end

(1..300_000_000).each do |n|
  puts "LMAO!"
end

underscore in `irb`

# %w(a b c).map(&:succ)
["b", "c", "d"]

# _
["b", "c", "d"]

# letters = _
["b", "c", "d"]

string concatenation

# "ab" + "cd"
"abcd"

# "ab" "cd"
"abcd"

string interpolation, normal

a = 2
b = "1#{a}3"
p b

123

string interpolation, also normal

@a = 5
b = "4#{@a}6"
p b

456

string interpolation, WTF?

@a = 8
b = "#@a"
c = "7#@a"
d = "7#@a9"
p b
p c
p d

8
78
7

interpolate into symbols

p :this_is_a_symbol.object_id

klass = "symbol"
p :"this_is_a_#{klass}".object_id

333788
333788

string delimiters

"String!"
'String!'
%{String!}
%|String!|
%`String!`
%;String!;

`String#*`

# "*" * 80
********************************************************************************

`DATA` and `END`

$ cat data.rb
p YAML.load(DATA.read)[ARGV.first]
__END__
foo: "Bar"
baz: "LOL!"

$ ruby -ryaml data.rb
nil

$ ruby -ryaml data.rb foo
"Bar"

$ ruby -ryaml data.rb bar
"LOL!"

`redo`

# s = ''
""

# 1.upto(5) { |i| s << i.to_s; redo if s.size < 3 }
1

# s
"1112345"

pulling elements out of arrays

# args = [1, 2, 3]
# first, *rest = args
# first
1

# rest
[2, 3]

splat arguments, anywhere (1.9+)

# def foo(*args); p args; end
# foo(1, 2, 3, 4)
[1, 2, 3, 4]

# def bar(first, *args); p first; p args; end
# bar(1, 2, 3, 4)
1
[2, 3, 4]

# def baz(first, *args, last); p first; p args; p last; end
# baz(1, 2, 3, 4)
1
[2, 3]
4

destructuring arrays

def touch_down
  yield [3, 7]
  puts "touchdown!"
end

touch_down do |(first_down, second_down)|
  puts "#{first_down} yards on the run"
  puts "#{second_down} yards passed"
end

3 yards on the run
7 yards passed
touchdown!

`Enumerable#any? / #all?`

# [false, false, true].any?
true

# [false, false, nil].any?
false

# [true, true, true].all?
true

# [true, true, false].all?
false

`Hash#new` with a block

# smash = Hash.new { |hash, key|
    hash[key] = "a #{key} just got SMASHED!" }
{}

# smash[:plum] = "cannot smash."
{:plum=>"cannot smash."}

# smash[:watermelon]
{:plum=>"cannot smash.",
  :watermelon=>"a watermelon just got SMASHED!"}

`Hash::[]`

# Hash[:apples, 3, :bananas, 2]
{:apples=>3, :bananas=>2}

# Hash[[:apples, 3, :bananas, 2] * 300_000]
SystemStackError: stack level too deep

Ruby bug warning!

`j` and `jj` (1.9+)

# require 'json'
# h = {a: 1, b:2}
{:a=>1, :b=>2}

# j(h)
{"a":1,"b":2}

# jj(h)
{
  "a": 1,
  "b": 2
}

z, ?	toggle help (this)
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stupid ruby tricks

and some useful ones

Nick Quaranto @qrush

ruby -c: Syntax checking

ruby -w: Indent checking (1.9+)

ruby -p, -e, -i

underscores in numbers

underscore in irb

string concatenation

string interpolation, normal

string interpolation, also normal

string interpolation, WTF?

interpolate into symbols

string delimiters

String#*

DATA and __END__

redo

pulling elements out of arrays

splat arguments, anywhere (1.9+)

destructuring arrays

Enumerable#any? / #all?

Hash#new with a block

Hash::[]

j and jj (1.9+)

thanks!

`ruby -c`: Syntax checking

`ruby -w`: Indent checking (1.9+)

`ruby -p, -e, -i`

underscore in `irb`

`String#*`

`DATA` and `END`

`redo`

`Enumerable#any? / #all?`

`Hash#new` with a block

`Hash::[]`

`j` and `jj` (1.9+)