CODEWITHSUNDEEP
typescript
Joff
Joff

Reputation: 12197

how to cast this function type in typescript

I get confused about how to do this kind of type casting in TS. I am defining a class method that needs to be this type (https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/types/react-big-calendar/index.d.ts#L229)

and I am trying to do something like this...

  public onSelectSlot: Pick<BigCalendarProps<InterviewEvent>, 'onSelectSlot'> = (slot) => {
    this.setCreateDialog(true, slot.slots.slice(0, -1));
  }

but that is not working and I cannot figure out how to pull the function arg type out of that interface in the link. How can I go about doing this?

Upvotes: 1

Views: 1917

Answers (2)

郭一凡
郭一凡

Reputation: 36

Pick returns a set of properties

type Pick<T, K extends keyof T> = { [P in K]: T[P]; }

So if you want to get a propertie,you need to provide the key of propertie like this

public onSelectSlot: Pick<
    BigCalendarProps<InterviewEvent>,
    'onSelectSlot'
  >['onSelectSlot'] = slot => {};

Or you can define a type alias

type PickPropertie<T, K extends keyof T> = T[K];

and use it.

public onSelectSlot: PickPropertie<
    BigCalendarProps<InterviewEvent>,
    'onSelectSlot'
  > = slot => {};

Upvotes: 0

Titian Cernicova-Dragomir
Titian Cernicova-Dragomir

Reputation: 250366

You are using Pick, that will not return the type of the proeprty but rather an object type with the picked properties.

You can use a type query to get the type of onSelectSlot.

  public onSelectSlot: BigCalendarProps<InterviewEvent>['onSelectSlot'] = (slot) => {
    this.setCreateDialog(true, slot.slots.slice(0, -1));
  }

Upvotes: 2

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