How do i type property as provided type
I'm making my property implementation and i need to get access to instance's property using just name of it. in roblox studio you can just do Instance[property_name] and it will return property, but how i can do it in ts?
52 Replies
you have to be more specfic with the typings for connect_to, string is too general
but then ill need to list every possible property, no?
do you need every possible property?
and you can use the InstanceProperties<T> utility type
ye i am
oh i think it would help
mhm, just give it the Instance you want the properties for
there is also much more if you are interested https://roblox-ts.com/docs/api/utility-types#writablepropertynamest
keyof WriteableInstanceProperties<YourInstance>it helped, now it even autofills properties, but how do i add property name to property chaned signal? it still thinks that this instance have only like 4 properties even tho i typed this instance as provided instance
what is the type of
this.instance
ConnectedInstance is
ProvidedInstance extends Instance
should i give you full code?
yes
export interface _SepartaredProperty<T> {
readonly name: string;
value: T;
changed: RBXScriptSignal;
Set: (this: SepartaredProperty<T>, value: T) => void;
Get: (this: SepartaredProperty<T>) => T;
Behaviours: {
OnTick: (this: void) => void;
OnChanged: (this: void, new_value: T) => void;
CanSet: (this: void) => boolean;
};
SetBehaviour: (
this: void,
behaviour_to_set: "OnTick" | "OnChanged" | "CanSet",
new_behaviour: (this: void) => boolean | void,
) => void;
}
export interface _ConnectedProperty<T, ConnectedInstance extends Instance> extends _SepartaredProperty<T> {
instance: ConnectedInstance;
connected_to: keyof WritableInstanceProperties<ConnectedInstance>;
override: boolean;
}
export class SepartaredProperty<T> implements _SepartaredProperty<T> {
readonly name: string;
value: T;
changed: RBXScriptSignal<Callback>;
SetBehaviour: (
this: void,
behaviour_to_set: "OnTick" | "OnChanged" | "CanSet",
new_behaviour: (this: void) => boolean | void,
) => void;
Behaviours: {
OnTick: (this: void) => void;
OnChanged: (this: void, new_value: T) => void;
CanSet: (this: void) => boolean;
};
protected _changed_bind: BindableEvent<Callback>;
constructor(name: string, value: T) {
this.name = name;
this.value = value;
this._changed_bind = new Instance("BindableEvent");
this.changed = this._changed_bind.Event;
this.SetBehaviour = function () {};
this.Behaviours = {
OnTick() {},
OnChanged(new_value) {},
CanSet() {
return true;
},
};
this.changed.Connect((new_value) => {
this.Behaviours.OnChanged(new_value);
});
}
public Set(set_to: T) {
if (this.Behaviours.CanSet()) {
if (this.value === set_to) {
return true;
}
this.value = set_to;
this._changed_bind.Fire(this.value);
return true;
} else {
return true;
}
}
public Get() {
return this.value;
}
}
export class ConnectedProperty<T, ConnectedInstance extends Instance>
extends SepartaredProperty<T>
implements _SepartaredProperty<T>
{
instance: ConnectedInstance;
connected_to: keyof WritableInstanceProperties<ConnectedInstance>;
override: boolean;
constructor(
Name: string,
Value: T,
ConnectToInstance: ConnectedInstance,
InstancesPropertyName: keyof WritableInstanceProperties<ConnectedInstance>,
Override: boolean,
) {
super(Name, Value);
this.instance = ConnectToInstance;
this.connected_to = InstancesPropertyName;
this.override = Override;
this.changed.Connect((new_value) => {
this.instance[InstancesPropertyName] = new_value;
});
this.instance.GetPropertyChangedSignal(InstancesPropertyName).Connect();
}
}
i started learning ts and flamework like yesterday so theres will be alot strange thingsthis.instance[PropertyName as never]
I think will help
Esp
this.instance[PropertyName as never] = new_value as never
it looks like it helped thank you!! Is it possible for you to explain why? i dont really understand
playground link
please don't never cast
this is a bad practice
never casting is basically ignoring the type system
ohhh ok
here's the solution
Fair, as quick fix I think it could work if the type is hard
it couldn't infer RBXObject properly
so i helped it a bit by passing it into a generic argument
this.instance.GetPropertyChangedSignal<ConnectedInstance>(InstancesPropertyName)i see now
thank you so much!
when i try to get instances property value it gives an error. Ts dont count this property as T. How do i type it to be same type as T?
what does
extends SepartaredProperty<ConnectedInstance[Name]> mean? Like why you putting Name in square bruckets?indexing a type
basically
Name is the property name and Instance[Name] is the property valueooooohhhh i seee
thanks youu😊
ohh it seem like still not working or i did something wrong?
it gives really long error explanation
Hear me out, when you know it's correct and don't want to bother with solving 1 page type error, prob
as never could be in handy
🥲i'm making this property implementation first of all to learn typescript, and i want to make it as good as possible using good practises so i can learn better. I want not to fix it, but to understand why it happens. Its really hard to understand what happening in ts rn so im asking others
Oh I see
Yeah fair
So again, what is this code for?
Cause I don't see highlight on the phone
Can you send screenshot
this is my property implementation and code erroring is code trying to get instance's property and set property class's value to it
screenshot of what
What is the use case?
like for example you create ConnectedProperty named WalkSpeed and connect it to player's walkspeed
and then
this property have diffrent behaviours
such as CanSet, OnTIck, OnChanged
and when this property value changes player's walkspeed will change too
or you can create property and have it like class itself
in a script
Does it sync between server and client?
Or you just want only 1 thing responsible for 1 property?
And do you use flamework?
noo its just an class
yes
Prob you don't need it the class wrapper for property?
If you need it e.g. for the character, prob it's better to use controller to set and manage the walk speed, charm for observable variables and to add component to the character that will apply the walk speed
Or you could go without Flamework component
But i said already that im making it almost only for learning reasons😭
oki
thanks you very much for trying to help still!!
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I know it, but i dont really know how to make so ConnectedInstance[Name] returns right type
change InstancePropertyName to be Name
so
InstancePropertyName: Nameoh
omg
solution was so easy
tysm!!!
all good
do you understand what the solution means?
yesss, but i dont understand how i didnt came to it
happens ❤️
wow, now if you give to new Property value diffrent from value of property you connecting it to it gives you an error, i love ts