Aug 2023
On TypeScript you can easily create the union of two similar, yet distinct, types:
Oscar Francotype iOSPaymentInfo = {
orderId: string;
iOSOnlyField: string;
}
type AndroidPaymentInfo = {
orderId: string;
androidOnlyField: string;
}
type PaymentInfo = iOSPaymentInfo | AndroidPaymentInfo;
// Trouble comes
let paymentInfo: PaymentInfo = ... // some payment info
// You cannot access iOSOnlyField or AndroidOnlyField TypeScript will complain the field might be null
paymentInfo.iOSOnlyField // kaboom
You can make typescript happy by adding a literal field that will provide it with enough info to make sure the object is correct:
type iOSPaymentInfo = {
orderId: string;
iOSOnlyField: string;
kind: 'iOS';
}
type AndroidPaymentInfo = {
orderId: string;
androidOnlyField: string;
kind: 'Android';
}
type PaymentInfo = iOSPaymentInfo | AndroidPaymentInfo;
// Trouble comes
let paymentInfo: PaymentInfo = ... // some payment info
if(paymentInfo.kind === 'iOS') {
// Type safe code for iOSPaymentInfo
} else {
// Type safe code for AndroidPaymentInfo
}