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Use string literal type for action type #64

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Aug 13, 2018
Merged

Use string literal type for action type #64

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2 changes: 1 addition & 1 deletion index.d.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,7 @@ declare module 'connected-react-router' {
action: 'POP' | 'PUSH'
}

export const LOCATION_CHANGE: string
export const LOCATION_CHANGE: '@@router/LOCATION_CHANGE'
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Why do we need to change this? How does it affect the result?

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This is needed for TypeScript's control flow analysis, e.g.:

const reducer = (state, action: LocationChangeAction | MyOtherAction) => {
  switch (action.type) {
    case LOCATION_CHANGE: {
      // Here, TypeScript knows `action` is type `LocationChangeAction`, and has a property called `payload`, which has a property called `location`
    }
  }
}

If the action type was not a string literal, TypeScript's control flow analysis wouldn't be able to narrow the union.

export const CALL_HISTORY_METHOD: string

export function push(path: Path, state?: LocationState): Action
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