README
NAME
WriteOnceHash - be a Hash in which each key can only be set once
SYNOPSIS
use WriteOnceHash;
# bind to predefined class
my %woh is WriteOnceHash;
%woh<a> = 5; # ok
%woh<a> = 1; # throws
CATCH {
when X::Hash::WriteOnce {
say "Sorry, already set {.key} before";
.resume
}
}
# mix in role on anything that does Associative
my %owoh{Any} does WriteOnce;
DESCRIPTION
This module makes an WriteOnceHash
class available that can be used instead of the normal Hash
. The only difference with a normal Hash
is, is that if an attempt is made to set the value of a key that has already been set before, an exception is thrown rather than just overwriting the key in the Hash
.
Also binding to non-existing keys in the hash, and then assigning to the obtained container, will only work once. Iterating over values of the hash will only yield values, not containers (as a normal Hash
would).
Also exports a X::Hash::WriteOnce
error class that will be thrown if an attempt is made to set a key again.
The underlying WriteOnce
role is also exported that can be used on objects that perform the Associative
role that are not Hash
(such as object hashes).
AUTHOR
Elizabeth Mattijsen [email protected]
Source can be located at: https://github.com/lizmat/WriteOnceHash . Comments and Pull Requests are welcome.
COPYRIGHT AND LICENSE
Copyright 2018, 2020, 2021 Elizabeth Mattijsen
This library is free software; you can redistribute it and/or modify it under the Artistic License 2.0.