方法级联语法

Question

Dart和Smalltalk有方法级联.

似乎可以通过类似的风格来实现do with.

例如,这是一个简单的程序,它使用GTK::Simple:

use v6;

use GTK::Simple;

my $app = GTK::Simple::App.new(title => "abc");

$app.set-content(
    GTK::Simple::VBox.new(
        my $button_a = GTK::Simple::Button.new(label => 'bcd'),
        my $button_b = GTK::Simple::Button.new(label => 'cde')
    )
);

$app.border-width = 20;

$button_a.clicked.tap({ .sensitive = False; $button_b.sensitive = True });

$button_b.sensitive = False;

$button_b.clicked.tap({ $app.exit });

$app.run;

这是do with在几个地方使用的等效程序,以实现类似于方法级联的效果:

use v6;

use GTK::Simple;

my $app;
my $button_a;
my $button_b;

do with GTK::Simple::App.new(title => 'abc')
{
    $app = $_;

    .set-content(
        GTK::Simple::VBox.new(
            $button_a = do with GTK::Simple::Button.new(label => 'bcd')
            {
                .clicked.tap({ .sensitive = False; $button_b.sensitive = True });
                $_
            },
            $button_b = do with GTK::Simple::Button.new(label => 'cde')
            {
                .sensitive = False;
                .clicked.tap({ $app.exit });
                $_
            }
        )
    );

    .border-width = 20;
    .run;
};

我的问题是,在Perl 6中表达方法级联风格是否有更惯用的方法？

缺点do with是您必须明确地返回$_.使用传统方法级联,隐式返回原始接收器对象.

例如,这是如何$button_a设置:

$button_a = do with GTK::Simple::Button.new(label => 'bcd')
{
    .clicked.tap({ .sensitive = False; $button_b.sensitive = True });
    $_
}

如果$_不必明确地返回它将是很好的.例如,类似于:

$button_a = do cascade GTK::Simple::Button.new(label => 'bcd')
{
    .clicked.tap({ .sensitive = False; $button_b.sensitive = True });
}

另一个缺点do with是语法比Dart和Smalltalk方法级联语法更重要.更接近Dart风格的东西可能如下所示:

$button_a = GTK::Simple::Button.new(label => 'bcd')
    ..clicked.tap({ .sensitive = False; $button_b.sensitive = True });

Answer 1

https://docs.raku.org/routine/andthen

my $obj = IO::Path.new($*CWD) andthen do { .say; 42 }; say $obj.perl