matriz en Hash de pares de valores clave en rubí

Question

De un modelo que devuelve todos los valores de una tabla, ¿cómo iba a convertir eso a un hash de pares de nombre y valor

{column_value => column_value} 

por ejemplo,

[{:id => 1, :name => 'first'}, {:id => 2, :name => 'second'}, {:id => 3, :name => 'third'}] 

a (especificando: Identificación y: nombre)

{'first' => 1, 'second' => 2, 'third' => 3} 

Answer 1

El siguiente enfoque es razonablemente compacta, sin embargo, sigue siendo legible:

def join_rows(rows, key_column, value_column) 
    result = {} 
    rows.each { |row| result[row[key_column]] = row[value_column] } 
    result 
end 

Uso:

>> rows = [{:id => 1, :name => 'first'}, {:id => 2, :name => 'second'}, {:id => 3, :name => 'third'}] 
>> join_rows(rows, :name, :id) 
=> {"third"=>3, "second"=>2, "first"=>1} 

O, si quieres una sola línea:

>> rows.inject({}) { |result, row| result.update(row[:name] => row[:id]) } 
=> {"third"=>3, "second"=>2, "first"=>1} 

Answer 2

o = Hash.new 
a = [{:id => 1, :name => 'first'}, {:id => 2, :name => 'second'}, {:id => 3, :name => 'third'}] 
a.each {|h| o[h[:name]] = h[:id] } 

puts o #{'third' => 3, 'second' => 2, 'first' => 1} 

Answer 3

Puede hacerlo en una línea con inject:

a = [{:id => 1, :name => 'first'}, {:id => 2, :name => 'second'}, {:id => 3, :name => 'third'}] 
a.inject({}) { |sum, h| sum.merge({ h[:name] => h[:id]}) } 
# => {"third" => 3, "second" => 2, "first" => 1}