多态 – Perl 6和`multi method new`

我有一个封装Int的类Price.我也希望它有Num和Str的构造函数.我认为我可以通过使Price :: new成为具有各种类型约束的多方法来实现这一点,但这不是我期望的行为.看起来Price.new正在完全跳过构造函数并直接进入BUILD,绕过了构建逻辑.

我知道通过查看其他Perl 6代码,使用multi方法new是可以接受的.但是,我还没有找到具有不同类型约束的多态构造函数的示例.如何重写此代码以强制它在构造函数中使用转换逻辑？

LIB / Price.pm6

#!/usr/bin/env perl6 -w

use v6;

unit class Price:ver<0.0.1>;

class X::Price::PriceInvalid is Exception {
    has $.price;

    method message() {
        return "Price $!price not valid"
    }
}

# Price is stored in cents USD
has $.price;

multi method new(Int $price) {
    say "Int constructor";
    return self.bless(:$price);
}

multi method new(Num $price) {
    say "Num constructor";
    return self.new(Int($price * 100));
}

multi method new(Str $price) {
    say "String constructor";
    $price .= trans(/<-[0..9.]>/ => '');
    unless ($price ~~ m/.d**2$/) {
        die(X::Price::PriceInvalid(:$price));
    }
    return self.new(Num($price));
}

submethod BUILD(:$!price) { say "Low-level BUILD constructor" }

method toString() {
    return sprintf("%.2f",($!price/100));
}

吨/ price.t

#!/usr/bin/env perl6 -w

use v6;
use Test;

use-ok 'Price','Module loads';
use Price;

# test constructor with Int
my Int $priceInt = 12345;
my $priceIntObj = Price.new(price => $priceInt);
is $priceIntObj.toString(),'123.45','Price from Int serializes correctly';

# test constructor with Num
my $priceNum = Num.new(123.45);
my $priceNumObj = Price.new(price => $priceNum);
is $priceNumObj.toString(),'Price from Num serializes correctly';

# test constructor with Num (w/ extra precision)
my $priceNumExtra = 123.4567890;
my $priceNumExtraObj = Price.new(price => $priceNumExtra);
is $priceNumExtraObj.toString(),'Price from Num with extra precision serializes correctly';

# test constructor with Str
my $priceStr = '$123.4567890';
my $priceStrObj = Price.new(price => $priceStr);
is $priceStrObj.toString(),'Price from Str serializes correctly';

# test constructor with invalid Str that doesn't parse
my $priceStrInvalid = 'monkey';
throws-like { my $priceStrInvalidObj = Price.new(price => $priceStrInvalid) },X::Price::PriceInvalid,'Invalid string does not parse';

done-testing;

PERL6LIB的输出= lib / perl6 t / price.t

ok 1 - Module loads
Low-level BUILD constructor
ok 2 - Price from Int serializes correctly
Low-level BUILD constructor
not ok 3 - Price from Num serializes correctly
# Failed test 'Price from Num serializes correctly'
# at t/price.t line 18
# expected: '123.45'
#      got: '1.23'
Low-level BUILD constructor
not ok 4 - Price from Num with extra precision serializes correctly
# Failed test 'Price from Num with extra precision serializes correctly'
# at t/price.t line 24
# expected: '123.45'
#      got: '1.23'
Low-level BUILD constructor
Cannot convert string to number: base-10 number must begin with valid digits or '.' in '?$123.4567890' (indicated by ?)
  in method toString at lib/Price.pm6 (Price) line 39
  in block <unit> at t/price.t line 30

:( Int $)
:( Num $)
:( Str $)

:( :price($) )

proto method new (|) {*}

proto method new ($) {*}

multi method new (Int :$price!){…}

multi submethod BUILD (Int :$!price!) {
    say "Int constructor";
}

multi submethod BUILD (Num :$price!) {
    say "Num constructor";
    $!price = Int($price * 100); 
}

multi submethod BUILD (Str :$price!) {
    say "String constructor";
    $price .= trans(/<-[0..9.]>/ => '');
    unless ($price ~~ m/.d**2$/) {
        die(X::Price::PriceInvalid(:$price));
    }
    $!price = Int($price * 100);
}

unit class Price:ver<0.0.1>;

class X::Price::PriceInvalid is Exception {
    has $.price;

    method message() {
        return "Price $!price not valid"
    }
}

# Price is stored in cents USD
has Int $.price is required;

method price () {
    $!price / 100; # return a Rat
}

# Real is all Numeric values except Complex
multi submethod BUILD ( Real :$price ){
    $!price = Int($price * 100);
}

multi submethod BUILD ( Str :$price ){
    $price .= trans(/<-[0..9.]>/ => '');
    unless ($price ~~ m/.d**2$/) {
        X::Price::PriceInvalid(:$price).throw;
    }
    $!price = Int($price * 100);
}

method Str() {
    return sprintf("%.2f",($!price/100));
}