Given the following hash: h = {"abc" => {32 => "xyz"}, 37 => :hello} if I extract the value of key "abc", I get: h["abc"] # => {32 => "xyz"} typeof(h["abc"]) # => (Hash(Int32, String) | Symbol) I’d like to convert h["abc"] type to : Hash(Int32, String) which is the type of {32 => "xyz"} I’m s…

You can straight up convert it using h["abc"].as(String), but I’d suggest using a better data type instead, like a Tuple or a record.

h["abc"].as(String) ends in an error Error: can’t cast (Hash(Int32, String) | Symbol) to String I could, of course, use the syntax h["abc"].as(Hash(Int32, String)) in this example, but that presupposes that I know the exact contents of the hash. I’m actually looking for a way to obtain a new …

[image] hutou: perhaps this isn’t possible with the current Hash API I think so.

[image] hutou: I’m actually looking for a way to obtain a new hash, the type of which is based solely on its content, and not on its origin. Ok, then something like case v = h["abc"] when Hash # do something hashy with v else # do something else end could perhaps work. But really, the …

Not easy to explain! The hash is used to parameterize the operation of an application and is in the user’s hands. The hash structure is not really unknown, but can be more or less complete, depending on the user’s use. The original idea was to facilitate programming by taking into account only th…

Hm, how does the user configuration get into the hash, though?

In fact, the application in question is a library, still in the development phase, designed for Crystal developers to format tables in Terminal mode (a primitive version of Tablo was released in 2021). To use this library, the developer builds and fills the hash as part of his own application. To …

[image] hutou: To use this library, the developer builds and fills the hash as part of his own application. It seems like a configuration class could be a much better option for this… Bringing type-safety, easy discoverability and documentation. Nested hashes are a bit frowned upon in Crysta…

Much better, indeed ! Thanks for the advice.

Hash and type restriction on extracted sub-hash

Help & Support

straight-shoota January 14, 2024, 6:30pm 6

It could maybe help to give some context why you end up with a nested hash of unknown structure and then want to import it into strict types in the first place.

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Hash and type restriction on extracted sub-hash

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