Implementing NSCopying automatically

Let's create an AutoCopy.stencil protocol, so that Article copy implementation can be generated using Sourcery:

{% for type in types.implementing.AutoCopy %}
extension {{ type.name }}: NSCopying {
    func copy(with zone: NSZone? = nil) -> Any {
        return {{type.name}}(
        {% map type.variables into vars using var %}
            {{ var.name }}: {{ var.name }}{% endmap %}
        {{ vars|join:"," }})
    }
}
{% endfor %}

It will generate the following AutoCopy.generated.swift:

extension Article: NSCopying {
    func copy(with zone: NSZone? = nil) -> Any {
        return Article(
            id: id,
            title: title,
            contents: contents,
            author: author,
            date: date,
            views: views)
    }
}

As you may have noticed, this is a simple implementation where the array's contents are not copied through the NSCopying protocol. Recursively, all objects that are copied should be copied by calling the .copy() method, if available.