How do I compare two hashes?
If you want to get what is the difference between two hashes, you can do this:
h1 = {:a => 20, :b => 10, :c => 44}
h2 = {:a => 2, :b => 10, :c => "44"}
result = {}
h1.each {|k, v| result[k] = h2[k] if h2[k] != v }
p result #=> {:a => 2, :c => "44"}
You can compare hashes directly for equality:
hash1 = {'a' => 1, 'b' => 2}
hash2 = {'a' => 1, 'b' => 2}
hash3 = {'a' => 1, 'b' => 2, 'c' => 3}
hash1 == hash2 # => true
hash1 == hash3 # => false
hash1.to_a == hash2.to_a # => true
hash1.to_a == hash3.to_a # => false
You can convert the hashes to arrays, then get their difference:
hash3.to_a - hash1.to_a # => [["c", 3]]
if (hash3.size > hash1.size)
difference = hash3.to_a - hash1.to_a
else
difference = hash1.to_a - hash3.to_a
end
Hash[*difference.flatten] # => {"c"=>3}
Simplifying further:
Assigning difference via a ternary structure:
difference = (hash3.size > hash1.size) \
? hash3.to_a - hash1.to_a \
: hash1.to_a - hash3.to_a
=> [["c", 3]]
Hash[*difference.flatten]
=> {"c"=>3}
Doing it all in one operation and getting rid of the difference
variable:
Hash[*(
(hash3.size > hash1.size) \
? hash3.to_a - hash1.to_a \
: hash1.to_a - hash3.to_a
).flatten]
=> {"c"=>3}
You can try the hashdiff gem, which allows deep comparison of hashes and arrays in the hash.
The following is an example:
a = {a:{x:2, y:3, z:4}, b:{x:3, z:45}}
b = {a:{y:3}, b:{y:3, z:30}}
diff = HashDiff.diff(a, b)
diff.should == [['-', 'a.x', 2], ['-', 'a.z', 4], ['-', 'b.x', 3], ['~', 'b.z', 45, 30], ['+', 'b.y', 3]]