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typescriptinterfaceschemaxortypescript2.0

TypeScript interface with XOR, {bar:string} xor {can:number}

How do I say that I want an interface to be one or the other, but not both or neither?

interface IFoo {
    bar: string /*^XOR^*/ can: number;
}
Solution

  • You can use union types along with the never type to achieve this:

    type IFoo = {
  bar: string; can?: never
} | {
  bar?: never; can: number
};


let val0: IFoo = { bar: "hello" } // OK only bar
let val1: IFoo = { can: 22 } // OK only can
let val2: IFoo = { bar: "hello",  can: 22 } // Error foo and can
let val3: IFoo = {  } // Error neither foo or can