Typescript - Parameter in Function Expression

Question

I have this code - where I'm trying to pass in a string title:

let GetData: (title: string) => Promise<APIStates<Series[]>>;

if (process.env["REACT_APP_SERVICE_VERSION"] === "development") {
    GetData = useGetDataServiceDummy(title)
}

However I keep getting 2 errors and can't figure out the syntax to resolve it:

Cannot find name 'title'
Promise<APIStates<Series[]> is not assignable to (title: string) => Promise<APIStates<Series[]>

Could someone please help me with the syntax to get around this error.

And for reference useGetDataServiceDummy

export async function useGetDataServiceDummy(title: string): Promise<APIStates<Series[]>> {
    // do soemthing with `title`
    return { status: "loaded", payload: dummyData };
}

Any help would be appreciated.

Thanks.

You've defined GetData as a function, but assigning to it the promise (the function's return value) — Aleksey L.
– Aleksey L., Commented Sep 10, 2019 at 8:09
Regarding title - in shown part of code it is not defined.. — Aleksey L.
– Aleksey L., Commented Sep 10, 2019 at 8:15
1) You're saying useGetDataServiceDummy will return a Promise and it just returns a regular Object. 2) title is literally not defined in the snippet you provided 3) You're assigning a return type of a useGetDataServiceDummy to GetData by calling it .(title) and you said it will be a function and not a Promise => : (title: string) => Promise<APIStates<Series[]>> — Roberto Zvjerković
– Roberto Zvjerković, Commented Sep 10, 2019 at 9:17

lukasgeiter · Accepted Answer · 2019-09-10 08:55:39Z

2

It looks like you're trying to assign useGetDataServiceDummy to GetData, however what you're actually doing is calling useGetDataServiceDummy and then assigning the return value to GetData. Try this instead:

if (process.env["REACT_APP_SERVICE_VERSION"] === "development") {
    GetData = useGetDataServiceDummy
}

answered Sep 10, 2019 at 8:55

lukasgeiter

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3 Comments

userMod2 Over a year ago

Yep - think that was it - I didn't need useGetDataServiceDummy(title)

userMod2 Over a year ago

Although if I'm being fully honest, I don't understand how title gets passed to useGetDataServiceDummy`.

lukasgeiter Over a year ago

at some later point ` GetData` will get called with a title. Since you've assigned userGetDataServiceDummy to GetData that means the dummy function will be called.

Serhan C. · Accepted Answer · 2019-09-10 09:25:28Z

0

If you want to assign useGetDataServiceDummy(title) function to GetData you should change your definition of GetData like this;

let GetData: Promise<APIStates<Series[]>>;

edited Sep 10, 2019 at 9:25

answered Sep 10, 2019 at 9:09

Serhan C.

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