Attribute+XMLParser.swift

import Foundation
import SWXMLHash

extension Attribute {
    init(xml: XMLIndexer) throws {
        self.name = try xml.value(ofAttribute: "name")
        self.type = try AttributeType(stringValue: try xml.value(ofAttribute: "attributeType"))
        self.isScalar = xml.value(ofAttribute: "usesScalarValueType") ?? false
        self.isOptional = xml.value(ofAttribute: "optional") ?? false
        self.userInfo = try xml.userInfo()
    }
}

private extension AttributeType {
    private static let typesMapping: [String: AttributeType] = [
        "Boolean": .boolean,
        "Binary": .binary,
        "Date": .date,
        "Decimal": .decimal,
        "Double": .double,
        "Float": .float,
        "Integer 16": .integer16,
        "Integer 32": .integer32,
        "Integer 64": .integer64,
        "String": .string,
        "Transformable": .transformable
    ]

    init(stringValue: String) throws {
        guard let type = AttributeType.typesMapping[stringValue] else {
            throw UnknownAttributeTypeError(type: stringValue)
        }
        self = type
    }
}

private struct UnknownAttributeTypeError: Error, CustomStringConvertible {
    let type: String

    var description: String {
        return "Unexpected attribute type: '\(type)'"
    }
}