Ruby：如何遍历哈希项数组？

Question

irb> pp config
[{"file"=>"/var/tmp"},
 {"size"=>"1024"},
 {"modified"=>"03/28/2012"}]
=> nil

In the code,

config.each do |d|
  # then how to break d into (k, v)???
end

Answer 1

config.each do |items|
  items.each do |key, value|
    # e.g. key="file", value="/var/tmp", etc.
  end
end

Answer 2

Just do

config.each do |hash|
  (k,v),_ = *hash
end

Answer 3

Inspired by @Arup's answer , here's a solution that doesn't require a extra, unused variable in the parallel assignment:

config.each do |hash|
  key, value = hash.to_a[0]
end

to_a converts the hash into the same kind of array that you would get by using splat *hash , but you can actually index the first element of the array (ie the first key/value pair) with [0] this way, while trying to do so with splat (*hash) generates a syntax error (at least in Ruby version 2.1.1):

>> k,v = (*hash)[0]
SyntaxError: (irb):4: syntax error, unexpected ')', expecting '='
k,v = (*x)[0]
          ^
        from c:/RailsInstaller/Ruby1.9.3/bin/irb:12:in `<main>'
>>

Of course, depending on what you're going to do with the key and value variables, it might make your code shorter and more readable to use one of these standard block constructs:

config.each do |hash|
  hash.each { |key,value| puts "#{key}: #{value}" }
end

# or

config.each do |hash|
  hash.each do |key,value|
    puts "#{key}: #{value}"
  end
end