winter wyvern
This is specifically via jsdoc.
I'm trying to dynamically construct objects that share a base type with arguments that share a base type. But I apparently don't have the generics set up properly and I'm not sure what I'm missing to make this work.
This is a small example which omits any of the class functionality and most of the dat props, but shows the problem I'm running into.
tribal beaconBOT
claudekennilol#0
heady sentinel
make BaseData a union of your other *Data types
/** @typedef {FooData | BarData} BaseData */
jolly ether
Yeah, you basically need a fixed set of possible subtypes to narrow this way, @winter wyvern - if you don't, there could be some other BaseData extending class that has type: "foo".
If you don't want a fixed list of subtypes like that then you'd need to narrow some other way, either an explicit check like data instanceof Foo or something like a custom type guard.
winter wyvern
Yeah, you basically need a fixed set of possible subtypes to narrow this way, <@...
So I essentially need two base types? One to define the shared properties (just 'type' in this example), that the types extend, and then a second "base type" that's a union type of any implemented base type to use as arguments?
jolly ether
Pretty much, yeah.
Actually having type on your base contract maybe isn't that useful, but I'm assuming this is placeholder for something more useful.
Like in a non-class example you might see:
type BaseWhatever = {
someCommonProp: string;
}
type Foo = BaseWhatever & {
type: "foo",
fooProp: string;
}
type Bar = BaseWhatever & {
type: "bar",
barProp: string;
}
type Whatever = Foo | Bar;
Yeah that's more straightforward.. I was just trying to do it inline in the js files. I'll probably just define them in a .d.ts file
winter wyvern
Pretty much, yeah.
Here's a pared down version of my real implementation. It's closer, but I'm essentially getting the same thing.
(note that I have ts playground set to javascript. I have actual types declared at the top of the file. Even though the types say they're giving errors, due to how ts playground works, those types behave just as if they were declared properly)
tribal beaconBOT
claudekennilol#0
winter wyvern
jolly ether
@winter wyvern It looks like the issue there is the illegal syntax here:
type SkillChoiceData = BaseChoiceData & {
type: (typeof ConfigurationTypes)[keyof typeof ConfigurationTypes] = 'skill';
I think that should just be:
type SkillChoiceData = BaseChoiceData & {
type: "skill"
}
Weird, why is that illegal? I can't define its type alongside giving it a value?
By itself that's a legal type definition
fiery crag
you're trying to assign a value in a type?
Types are types, they aren't values and don't have values.
jolly ether
Weird, why is that illegal? I can't define its type alongside giving it a value?
Yeah, you don't define types for values of types; that's just not correct syntax.
You're ending up with type: "languge" | "skill", not type: "language" which is why it doesn't narrow when you check it in the runtime code.
Personally, I'd generally derive the type from the union:
tribal beaconBOT
type BaseChoiceData = {
// other common properties (not type)
};
type LanguageChoiceData = BaseChoiceData & {
type: 'language';
//... other fields
};
type SkillChoiceData = BaseChoiceData & {
type: 'skill';
//... other fields
};
type ChoiceData = LanguageChoiceData | SkillChoiceData;
type ChoiceType = ChoiceData["type"];
// ^? - type ChoiceType = "language" | "skill"
This is js so I still want a codified const to use instead of hardcoding strings throughout the code. So I was hoping to type it directly against the const from the js file. But you've given me enough to move forward with, thanks 👍
Though I guess I could define ChoiceType like you've laid out above and then type my actual code against it and that should give me the same result