Let us see a example:
interface Gender {
title: "male" | "female";
clothing: MaleClothing | FemaleClothing;
}
interface MaleClothing {
// some properties...
}
interface FemaleClothing {
// some properties...
}
Here Gender interface is a interface of unions and it has few problems such as title can be male with clothing FemaleClothing and title can be female with clothing MaleClothing. So it is error prone. In such cases, we can prefer union of interfaces as below:
interface Male {
title: "male";
clothing: MaleClothing;
}
interface Female {
title: "female";
clothing: FemaleClothing;
}
type Gender = Male | Female;
By using union of interfaces, we have eradicated the error that we had peviously.