Modeling Maps

[ericzbeard]

I'm wondering if it's possible to have a strongly typed map that lets me use object syntax, so I can avoid the extra typing involved with ["Key"] and just type Key, but the type of Value is still enforced. (To be clear, I need a map because the names of the keys are not known ahead of time)

Here's an example:

class Widget {
    Name: String
}

class A {
    Props: Mapping<String, Widget>
}

// Valid
a: A = new {
    Props {
        ["Foo"] {
            Name = "widget a"
        }
    }
}

// Valid
aa: A = new {
    Props {
        ["Foo"] = new Widget {
            Name = "widget aa"
        }
    }
}

// Invalid but this is what I want (less verbose)
aaa: A = new {
    Props {
        Foo {
            Name = "widget aaa"
        }
    }
}

[bioball]

This isn't possible; it was actually an intentional design goal to separate the grammar for these two. The intention is that you can unambiguously tell which keys are not fixed when reading through Pkl code.

[ericzbeard]

Thanks! Makes sense, just making sure I didn't miss anything.

[holzensp]

That said, you can fake it. If all of your values are of type Foo, you can say lightSyntaxFakeMapping: Dynamic(toMap().values.every((it) -> it is Foo))

[bioball]

That’s possible, although, I wouldn’t recommend it.

With this pattern, it’s not possible to define default, because it already exists on the class.

You also don’t have niceties like autocompletion and checking in the IDE.