Course of Raku / Advanced / Operators / Traits and pragmas 🆕 / Exercises / A custom trait

Solution: A custom trait

Here is a possible solution to the task.

Code

my %role;

multi sub trait_mod:<is>(Routine:D $r, :$role!) {
    %role{$r.name} = $role;
}

sub login() is role('admin') { }

say %role<login>;

🦋 You can find the source code in the file custom-trait.raku.

Output

admin

Comments

The trait is a multi sub trait_mod:<is> whose named parameter :$role! triggers it for is role(...). Unlike a presence-only trait, this one receives the argument: is role('admin') binds 'admin' to $role.
The body stores that value under the subroutine’s name. Reading %role<login> back afterwards gives admin. (Traits run at compile time, so the entry is already there by the time the program runs.)

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