ruby - Could any one walk me through this code? -

i'm getting confused iterations - walk me through code does? friends , family hashes , language ruby.

friends.each { |x| puts "#{x}" }  family.each { |x, y| puts "#{x}: #{y}" } 

friends.each { |x| puts "#{x}" }  family.each { |x, y| puts "#{x}: #{y}" } 

the first equivalent to:

x = [friends.keys[0], friends.values[0]] puts "#{x}" x = [friends.keys[1], friends.values[1]] puts "#{x}" x = [friends.keys[2], friends.values[2]] puts "#{x}" # ... x = [friends.keys[n], friends.values[n]] puts "#{x}" 

the second:

x = family.keys[0] y = family.values[0] puts "#{x}: #{y}" x = family.keys[1] y = family.values[1] puts "#{x}: #{y}" x = family.keys[2] y = family.values[2] puts "#{x}: #{y}" # ... x = family.keys[n] y = family.values[n] puts "#{x}: #{y}" 

any time have { |...| ... } or do |...|; ...; end after method, creating called block. block passed method, can yield parameters block. array#each call block each element; hash#each pass [key, value].

you could, of course, totally different, so:

def test   yield('oh my')   yield('i really')   yield('like blocks') end test { |a| puts } 

which outputs

oh blocks 

if yield array block, can assigned multiple or single parameter.

def test   yield(['oh', 'my'])   yield(['i', 'really'])   yield(['like', 'blocks']) end test { |a, b| puts "#{a}-#{b}" } 

which outputs

oh-my i-really like-blocks 

or, if accept single parameter in block, passed array

test { |a| puts a.inspect } 

outputs

["oh", "my"] ["i", "really"] ["like", "blocks"] 

so, array#each doesn't exist , want create yourself. like

class array   def each     = 0     while < length_of_underlying_array       next_element = get_element(i)       yield(next_element)     end   end end 

or, hash#each

class hash   def each     = 0     while < length_of_underlying_hash       next_key = keys[i]       next_value = values[i]       yield([next_key, next_value])     end   end end 

another general tip, since ruby open source, can see how array#each , hash#each implemented in c, matches plain ruby code above.