struct NamedTuple(**T)
Overview
A named tuple is a fixed-size, immutable, stack-allocated mapping of a fixed set of keys to values.
You can think of a NamedTuple as an immutable Hash whose keys (which
are of type Symbol), and the types for each key, are known at compile time.
A named tuple can be created with a named tuple literal:
language = {name: "Crystal", year: 2011} # NamedTuple(name: String, year: Int32)
language[:name] # => "Crystal"
language[:year] # => 2011
language[:other] # compile time errorThe compiler knows what types are in each key, so when indexing a named tuple with a symbol literal the compiler will return the value for that key and with the expected type, like in the above snippet. Indexing with a symbol literal for which there's no key will give a compile-time error.
Indexing with a symbol that is only known at runtime will return
a value whose type is the union of all the types in the named tuple,
and might raise KeyError.