Is there a way to redefine the old index signature when trying to extend an interface with different property types? I am encountering an error when adding new properties that have a different type from the original index signature.
interface A {
a: number;
b: string;
[key: string]: number | string;
}
interface B extends A {
c: Function;
}
Error: Property 'c' of type 'Function' is not assignable to string index type 'string | number'.ts(2411)
When B extends A, it indicates that B can be used in the same places where A is accepted.
If the definition is 'widened', not every instance of B will be compatible with A, which is not permitted.
To resolve these problems, it is advisable to avoid using the index signature excessively as it can lead to issues similar to using any.
You established a guideline regarding your keys in situation A, which requires compliance from party B
Try implementing type aliases for better code organization.
type B = A & {
c: Function;
};
From my understanding, there isn't a direct way to override the index signature when utilizing an interface. However, a workaround could involve using a type alias and intersection instead, as type aliases allow for properties to be overridden.
It's important to note that enabling the --strictFunctionTypes flag in typescript is necessary to ensure this approach functions correctly.
interface A {
a: number;
b: string;
[key: string]: number | string;
}
type B = A & {
c: Function;
}
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