如何从嵌套散列获取键值或键值的值？

Question

如何从嵌套哈希中获取密钥的值或密钥的存在？

例如：

a = { "a"=> { "b" => 1, "c" => { "d" => 2, "e" => { "f" => 3 } }}, "g" => 4} 

是否有任何直接的方法来获得 “F” 的值？或者有没有一种方法来知道嵌套散列中键的存在？

Answer 1

%w[a c e f].inject(a, &:fetch) # => 3 
%w[a c e x].inject(a, &:fetch) # > Error key not found: "x" 
%w[x].inject(a, &:fetch) # => Error key not found: "x" 

或者，避免发生错误：

%w[a c e f].inject(a, &:fetch) rescue "Key not found" # => 3 
%w[a c e x].inject(a, &:fetch) rescue "Key not found" # => Key not found 
%w[x].inject(a, &:fetch) rescue "Key not found" # => Key not found 

Answer 2

def is_key_present?(hash, key) 
    return true if hash.has_key?(key) 
    hash.each do |k, v| 
    return true if v.kind_of?(Hash) and is_key_present?(v, key) 
    end 
    false 
end 

> is_key_present?(a, 'f') 
=> true