How do I search within an array of hashes by hash values in ruby?

You're looking for Enumerable#select (also called find_all):

@fathers.select {|father| father["age"] > 35 }
# => [ { "age" => 40, "father" => "Bob" },
#      { "age" => 50, "father" => "Batman" } ]

Per the documentation, it "returns an array containing all elements of [the enumerable, in this case @fathers] for which block is not false."

this will return first match

@fathers.detect {|f| f["age"] > 35 }