Documentation for method keyof assembled from the following types:

class Hash

From Hash

(Hash) method keyof

Defined as:

method keyof()

Returns the type constraint for the keys of the invocant. For normal hashes the method returns the coercion type (Str(Any)) while for non-string keys hashes the type used in the declaration of the Hash is returned.

my %h1 = 'apples' => 3, 'oranges' => 7;  # (no key type specified) 
say %h1.keyof;                           # OUTPUT: «(Str(Any))␤» 
 
my %h2{Str} = 'oranges' => 7;            # (keys must be of type Str) 
say %h2.keyof;                           # (Str) 
%h2{3} = 'apples';                       # throws exception 
CATCH { default { put .^name, ': ', .Str } };
# OUTPUT: «X::TypeCheck::Binding: Type check failed in binding to key; expected Str but got Int (3)␤» 
 
my %h3{Int};                             # (this time, keys must be of type Int) 
%h3{42} = 4096;
say %h3.keyof;                           # (Int)

role Associative

From Associative

(Associative) method keyof

Defined as:

method keyof()

Returns the parameterized key used for the Associative role, which is Any coerced to Str by default. This is the class used as second parameter when you use the parameterized version of Associative.

my %any-hash;
%any-hash.keyof; #OUTPUT: «(Str(Any))␤»

role QuantHash

From QuantHash

(QuantHash) method keyof

method keyof()

Returns the type of value a key of this QuantHash may have. This is typically Mu.