Casting Types in TypeScript

Here is the TypeScript code I am using to create an ApolloClient:

return new ApolloClient({
    dataIdFromObject: (o) => o.uuid
});

Upon compilation, I encountered the following error message:

TS2339:Property 'uuid' does not exist on type 'Object'

To address this issue, I attempted to define a specific interface:

interface DomainObject {
    uuid: string
}
...
return new ApolloClient({
    dataIdFromObject: (<DomainObject>o) => o.uuid
});

However, this led to confusion and further errors in my code. In particular, the cast operation triggered the following error:

TS17008:JSX element '' has no corresponding closing tag

The compiler seems to interpret this as JSX code.

Can anyone suggest a solution to rectify this situation?

Thank you for your assistance.

Answer №1

It is important to note that type assertions are only valid on expressions. The variable o in this context is actually a parameter declaration, not an expression (as it is used in the lambda function o => o.uuid). However, you can still provide a type annotation for the parameter:

return new ApolloClient({
    dataIdFromObject: (o: DomainObject) => o.uuid
});

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