I need to force an array to have a specific set of values that should be then the keys of my interface. I can force the array with
type SomeProperties = ['prop1', 'prop2', 'prop3'];
but I don't know how to force an interface to have those properties. I tried something like
type MyInterface = {
[key in keyof SomeProperties]: string;
}
but obviously the keys of an array are just numbers so my interface become
interface MyInterface {
0: string;
1: string;
2: string;
}
instead of the wanted interface
interface MyInterface {
prop1: string;
prop2: string;
prop3: string;
}
Do you know if there is a way to achieve this in Typescript?
It would be useful because I need to iterate on some properties to "clone" an object and I also need to access to those properties easily. Repeating the properties in both type and interface is a bit fragile for me.
As you note, the strings you're trying to access aren't the keys of SomeProperties, but the elements of SomeProperties.
You can use the indexed access operator here: if K is a key (or a union of keys) of T, then T[K] is the property type (or union of property types) corresponding to accessing the K key(s) of T.
Tuples and arrays accept number as a key type, so you want to use SomeProperties[number] to give you the union "prop1"|"prop2"|"prop3":
type SomeProperties = ['prop1', 'prop2', 'prop3'];
type MyInterface = {
[K in SomeProperties[number]]: string;
}
const myInterface: MyInterface = {
prop1: 'this',
prop2: 'works',
prop3: 'now'
}