如果OpenStruct中不存在密钥，我该如何返回nil？(How can I return nil if a key does not exist in OpenStruct?)

如果OpenStruct中不存在密钥，我该如何返回nil？(How can I return nil if a key does not exist in OpenStruct?)

我有一个传递给OpenStruct的哈希，以便用a表示. 。 这非常有效。 但是当我尝试访问不存在的键时，会引发undefined method <unknown key> for #<Hash:0x7f24ea884210> (NoMethodError) 。 怎么能让它返回nil ？

如果我用原始哈希尝试相同的东西，我会得到nil但不是与OpenStruct ！

该程序的片段：

TXT_HASH = load_data("test.txt") pp TXT_HASH[:ftp][:lastname] ## print nil as lastname does not exist TXT = OpenStruct.new(TXT_HASH) pp TXT.ftp.lastname ## raises NoMethodError ## Can it return nil?

I have a hash that passed to OpenStruct in order to make it word with a .. This works perfectly. But when ever I try to access a key that does not exist undefined method <unknown key> for #<Hash:0x7f24ea884210> (NoMethodError) is raised. How can I make it return nil?

If I try the same thing with the original hash I get nil but not with OpenStruct!!

The snippet from the program:

TXT_HASH = load_data("test.txt") pp TXT_HASH[:ftp][:lastname] ## print nil as lastname does not exist TXT = OpenStruct.new(TXT_HASH) pp TXT.ftp.lastname ## raises NoMethodError ## Can it return nil?

最满意答案

OpenStruct不是递归的。 在这种情况下， TXT.ftp返回Hash，而不是OpenStruct，因此#lastname 。

如果需要，有一个名为recursive-open-struct的库。 像这样用它：

require 'recursive-open-struct' TXT = RecursiveOpenStruct.new(TXT_HASH) pp TXT.ftp.lastname #=> nil

OpenStruct is not recursive. In this case TXT.ftp returns a Hash, not an OpenStruct, so #lastname is not defined.

If you want, there is a library called recursive-open-struct. Use it like this:

require 'recursive-open-struct' TXT = RecursiveOpenStruct.new(TXT_HASH) pp TXT.ftp.lastname #=> nil