关于解析：如何使用Scala解析器组合器解析层次结构实体

How to parse hierarchical entities using Scala parser combinators

我正在尝试使用Scala解析器组合器解析实体以及组成该实体字段的实体。我想通过让每个子实体都知道如何解析自身来做到这一点。

我的问题可以由具有Address和Car的Person类重现。这是Address和Car类的外观以及它们的解析方式。

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25

import scala.util.parsing.combinator._

case class Address(val street: String, val postCode: String) {

}

object Address extends JavaTokenParsers {

def parse: Parser[Address] = (streetPattern ~ postCodePattern) ^^ {
case street ~ postCode => Address(street, postCode)
}

}

case class Car(val make: String, val model: String) {

}

object Car extends JavaTokenParsers {

def parse: Parser[Car] = (stringLiteral ~":" ~ stringLiteral) ^^ {
case make ~":" ~ model => Car(make, model);
}

}

我遇到问题的地方是当我尝试组合解析器以解析Person：

1
2
3
4
5
6
7
8
9
10
11

case class Person(val address: Address, val car: Car) {

}

object Person extends JavaTokenParsers {

def parse: Parser[Person] = (Address.parse ~ Car.parse) ^^ {
case address ~ car => Person(address, car);
}

}

我得到的编译器错误是这样的：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15

[error] Parser.scala:38: type mismatch;
[error] found : Car.Parser[Car]
[error] required: Address.Parser[?]
[error] def parse: Parser[Person] = (Address.parse ~ Car.parse) ^^ {
[error] ^
[error] Parser.scala:39: type mismatch;
[error] found : Any
[error] required: Address
[error] case address ~ car => Person(address, car);
[error] ^
[error] Parser.scala:39: type mismatch;
[error] found : Any
[error] required: Car
[error] case address ~ car => Person(address, car);
[error] ^

如何将两个解析器组合成可以解析完整的Person对象的解析器？