％w [acef] .inject（a，&：fetch）＃=> 3 
％w [a c e x] .inject（a，&：fetch）＃>找不到错误键：x
％w [x] .inject（a，&：fetch）＃=>找不到错误键：x
 

或者，为避免错误： $ b $ （a，&：fetch）rescueKey not found＃=> b

 ％w [acef] .inject （a，&：fetch）rescue找不到密钥＃=>未找到密钥
％w [x] .inject（a，&：fetch）rescueKey not found＃=>未找到密钥
 

How do I get the value of a key or the key's presence from a nested hash?

For example:

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

Is there any direct method to get the value of "f"? Or is there a method to know the presence of key in the nested hash?

%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"

Or, to avoid errors:

%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