Callbacks in Ruby

callback-block.rb

irb(main):001:0> class Foo
irb(main):002:1>   def set_callback(&block)
irb(main):003:2>     @callback = block
irb(main):004:2>   end
irb(main):005:1> 
irb(main):006:1*   def run
irb(main):007:2>     10.times do |n|
irb(main):008:3*       @callback.call(n) if @callback
irb(main):009:3>     end
irb(main):010:2> 
irb(main):011:2*     puts "complete"
irb(main):012:2>   end
irb(main):013:1> end
=> :run
irb(main):015:0> f = Foo.new
=> #<Foo:0x007fde7b9f3da8>
irb(main):016:0> f.run
complete
=> nil
irb(main):017:0> f.set_callback {|n| puts n }
=> #<Proc:0x007fde7b9e8408@(irb):17>
irb(main):018:0> f.run
0
1
2
3
4
5
6
7
8
9
complete
=> nil
irb(main):019:0> class Bar
irb(main):020:1>   def run
irb(main):021:2>     message = "hello world"
irb(main):022:2>     foo.set_callback { |n| puts "#{message} #{n}" }
irb(main):023:2>     foo.run
irb(main):024:2>   end
irb(main):025:1>   
irb(main):026:1*   def foo
irb(main):027:2>     @foo ||= Foo.new
irb(main):028:2>   end
irb(main):029:1> end
=> :foo
irb(main):030:0> b = Bar.new
=> #<Bar:0x007fde7ab237b0>
irb(main):031:0> b.run
hello world 0
hello world 1
hello world 2
hello world 3
hello world 4
hello world 5
hello world 6
hello world 7
hello world 8
hello world 9
complete
=> nil

callback-method.rb

irb(main):001:0> class Foo
irb(main):002:1>   attr_accessor :callback
irb(main):003:1> 
irb(main):004:1*   def run
irb(main):005:2>     10.times do |n|
irb(main):006:3*       callback.call(n) if callback
irb(main):007:3>     end
irb(main):008:2> 
irb(main):009:2*     puts "complete"
irb(main):010:2>   end
irb(main):011:1> end
=> :run
irb(main):012:0> 
irb(main):013:0* class Bar
irb(main):014:1>   def run
irb(main):015:2>     foo.callback = method(:tick)
irb(main):016:2>     foo.run
irb(main):017:2>   end
irb(main):018:1> 
irb(main):019:1*   def tick(n)
irb(main):020:2>     message = "hello world"
irb(main):021:2>     puts "#{message} #{n}"
irb(main):022:2>   end
irb(main):023:1> 
irb(main):024:1*   def foo
irb(main):025:2>     @foo ||= Foo.new
irb(main):026:2>   end
irb(main):027:1> end
=> :foo
irb(main):028:0> b = Bar.new
=> #<Bar:0x007ff74d338488>
irb(main):029:0> b.run
hello world 0
hello world 1
hello world 2
hello world 3
hello world 4
hello world 5
hello world 6
hello world 7
hello world 8
hello world 9
complete
=> nil