英文:
How to add an attribute and its accessors in Raku using add_attribute()?
问题
我有这个程序：
class Foo {has $.first;}my $a = Attribute.new(:name('$!second'),:type(Int),:package('Foo'),:has_accessor(True));Foo.^add_attribute($a);Foo.^compose;Foo.^attributes; # Mu $!firstInt $!secondmy $foo = Foo.new: :42first, :21second;$foo.second; # P6opaque: no such attribute '$!second' on type Foo in a Foo when trying to get a value
attributes 方法显示已添加属性，似乎成功创建了一个对象，但当我尝试访问 $!second 属性时，我收到一个错误。
我漏掉了什么？
英文:
I have this program:
class Foo {has $.first;}my $a = Attribute.new(:name('$!second'),:type(Int),:package('Foo'),:has_accessor(True));Foo.^add_attribute($a);Foo.^compose;Foo.^attributes».say; # Mu $!firstInt $!secondmy $foo = Foo.new: :42first, :21second;$foo.second.say; # P6opaque: no such attribute '$!second' on type Foo in a Foo when trying to get a value
The attributes method shows that the attribute has been added, creating an object apparently succeeds, yet when I try to access the $!second attribute I receive an error.
What am I missing?
答案1
得分: 7
我漏掉了什么吗？
看起来你没有漏掉任何东西。在我看来这是一个 bug。
在 RakuAST 开发的这个阶段，我认为它不太可能被修复。
如果你真的对以编程方式构建类感兴趣，我建议你开始研究如何使用 RakuAST。
文档仍然大部分缺失，但有一个强大的 .AST 方法，你可以在示例代码上运行它，它会生成创建该代码所需的 RakuAST 语句。例如：
$ raku -e 'say Q|class A { has $.a; has $.b }|.AST'RakuAST::StatementList.new(RakuAST::Statement::Expression.new(expression => RakuAST::Package.new(declarator => "class",name => RakuAST::Name.from-identifier("A"),body => RakuAST::Block.new(body => RakuAST::Blockoid.new(RakuAST::StatementList.new(RakuAST::Statement::Expression.new(expression => RakuAST::VarDeclaration::Simple.new(scope => "has",sigil => "$",twigil => ".",desigilname => RakuAST::Name.from-identifier("a"))),RakuAST::Statement::Expression.new(expression => RakuAST::VarDeclaration::Simple.new(scope => "has",sigil => "$",twigil => ".",desigilname => RakuAST::Name.from-identifier("b")))))))))
英文:
> What am I missing?
Looks like you're not missing anything. Looks like a bug to me.
At this stage of RakuAST development, I don't think it will get fixed.
If you're really into building classes programmatically, I'd suggest you start looking into using RakuAST.
Documentation is still mostly absent, but there's a powerful .AST method that you can run on sample code, that will produce the RakuAST statements needed to create that code. For example:
$ raku -e 'say Q|class A { has $.a; has $.b }|.AST'RakuAST::StatementList.new(RakuAST::Statement::Expression.new(expression => RakuAST::Package.new(declarator => "class",name => RakuAST::Name.from-identifier("A"),body => RakuAST::Block.new(body => RakuAST::Blockoid.new(RakuAST::StatementList.new(RakuAST::Statement::Expression.new(expression => RakuAST::VarDeclaration::Simple.new(scope => "has",sigil => "$",twigil => ".",desigilname => RakuAST::Name.from-identifier("a"))),RakuAST::Statement::Expression.new(expression => RakuAST::VarDeclaration::Simple.new(scope => "has",sigil => "$",twigil => ".",desigilname => RakuAST::Name.from-identifier("b")))))))))
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