What is the proper way to define the type of the state object in pinia?

Question

What is the proper way to define the type of the state object in pinia?

I am currently working on a chess game project using Vue 3 and TypeScript along with Pinia for state management.

Here is an example of what I want to implement:

export const useStore = defineStore("game", {
  state: () => {
    return {
      moves: [],
      gameBoard:  getInitialBoard(),
      playerTurn: PieceColor.White,
      previousPieceSelected: undefined
    }
  },
    updatePreviousPieceSelected(piece: Piece | undefined ) {
      this.previousPieceSelected = piece
    }
  }
})

UpdateGameState.vue

setup() {
    const store = useStore()
    const previousPieceSelected: Piece | undefined = store.previousPieceSelected;
    let playerTurn: PieceColor = store.playerTurn;

    const initialGameState: GameState = {
      boardState: store.gameBoard,
      playerTurn,
    };

    const updateGameState = (
      cellRow: number,
      cellCol: number,
      currentPiece: Piece
    ) => {
      
      if (
        previousPieceSelected === undefined ||
        previousPieceSelected.pieceType === PieceType.None
      ) {
        store.updatePreviousPieceSelected(currentPiece);
      }

      if (
        (previousPieceSelected !== currentPiece && (currentPiece.pieceType === PieceType.None || currentPiece.color !== previousPieceSelected.color)) 
      ) {
        MovePiece(store.gameBoard, previousPieceSelected, {row: cellRow, col: cellCol} as Position)
        store.updatePreviousPieceSelected(undefined);
        store.changePlayer();
      }
    };

However, I encountered an error on the following line:

store.updatePreviousPieceSelected(currentPiece);

The error states that currentPiece (of type Piece) is not assignable to type undefined. As a workaround, I made some changes in my store like so:

export const useStore = defineStore("game", {
  state: () => {
    return {
      moves: [],
      gameBoard:  getInitialBoard(),
      playerTurn: PieceColor.White,
      previousPieceSelected: getInitialPreviousPieceSelected()
    }
  },
  actions: {
    changePlayer() {
      this.playerTurn =
          this.playerTurn === PieceColor.White
            ? PieceColor.Black
            : PieceColor.White;
    },
    updatePreviousPieceSelected(piece: Piece | undefined ) {
      this.previousPieceSelected = piece
    }
  }
})

function getInitialPreviousPieceSelected(): Piece | undefined {
  return undefined;
}

Even though it works, it feels somewhat cumbersome. Is there a better way to type previousPieceSelected in the initial state return?

typescript vue.js vuejs3 pinia

Answer 1

Answer №1

The data type of this.previousPieceSelected is automatically determined by the initial state and is currently set to undefined, meaning its type is also undefined (which restricts it from being assigned any other value).

To specify a different type for the initial undefined value, you can utilize a type assertion (using the as keyword followed by the desired type like Piece | undefined).
Additionally, remember that optional parameters can be denoted with ?: instead of | undefined, offering a more concise notation.

export const useStore = defineStore("game", {
  state: () => {
    return {
      moves: [],
      previousPieceSelected: undefined as Piece | undefined, 1️⃣
    }
  },
  actions: {                          2️⃣
    updatePreviousPieceSelected(piece ?: Piece) {
      this.previousPieceSelected = piece
    }
  }
})

Answer 2

The data type of this.previousPieceSelected is automatically determined by the initial state and is currently set to undefined, meaning its type is also undefined (which restricts it from being assigned any other value).

To specify a different type for the initial undefined value, you can utilize a type assertion (using the as keyword followed by the desired type like Piece | undefined).
Additionally, remember that optional parameters can be denoted with ?: instead of | undefined, offering a more concise notation.

export const useStore = defineStore("game", {
  state: () => {
    return {
      moves: [],
      previousPieceSelected: undefined as Piece | undefined, 1️⃣
    }
  },
  actions: {                          2️⃣
    updatePreviousPieceSelected(piece ?: Piece) {
      this.previousPieceSelected = piece
    }
  }
})

Answer 3

Answer №2

or maybe even similar

interface IUserState {
  user: null | IUser
}
    
export const useUserStorage = defineStorage({
  id: 'user',
  state: (): IUserState => ({
    user: null,
  })
...

Answer 4

or maybe even similar

interface IUserState {
  user: null | IUser
}
    
export const useUserStorage = defineStorage({
  id: 'user',
  state: (): IUserState => ({
    user: null,
  })
...

Answer 5

Answer №3

defineStore is a versatile function found in TypeScript that takes in two parameters: the store ID and the state.

/**
 * This creates a `useStore` function to access the store instance
 *
 * @param id - unique identifier for the store
 * @param options - options for defining the store
 */
export declare function defineStore<Id extends string, S extends StateTree = {}, G extends _GettersTree<S> = {}, A = {}>(id: Id, options: Omit<DefineStoreOptions<Id, S, G, A>, 'id'>): StoreDefinition<Id, S, G, A>;

This allows for the precise definition of typed State and the name of the store.

import { defineStore } from 'pinia';

interface State {
  borks: string[];
  isWoof: boolean;
}

interface Getters {}

interface Actions {
  addBork: (bork: string) => void;
}

const useBorkStore = defineStore<'bork', State, Getters, Actions>('bork', {
  state: () => {
    return {
      borks: [],
      isWoof: false
    }
  },

  actions: {
    addBork(bork: string) {
      this.borks.push(bork);
    }
  }
})

export { useBorkStore };

Answer 6

defineStore is a versatile function found in TypeScript that takes in two parameters: the store ID and the state.

/**
 * This creates a `useStore` function to access the store instance
 *
 * @param id - unique identifier for the store
 * @param options - options for defining the store
 */
export declare function defineStore<Id extends string, S extends StateTree = {}, G extends _GettersTree<S> = {}, A = {}>(id: Id, options: Omit<DefineStoreOptions<Id, S, G, A>, 'id'>): StoreDefinition<Id, S, G, A>;

This allows for the precise definition of typed State and the name of the store.

import { defineStore } from 'pinia';

interface State {
  borks: string[];
  isWoof: boolean;
}

interface Getters {}

interface Actions {
  addBork: (bork: string) => void;
}

const useBorkStore = defineStore<'bork', State, Getters, Actions>('bork', {
  state: () => {
    return {
      borks: [],
      isWoof: false
    }
  },

  actions: {
    addBork(bork: string) {
      this.borks.push(bork);
    }
  }
})

export { useBorkStore };

Answer 7

Answer №4

If the information isn't loading properly.

Check out:

Alternatively, you can try:

import {defineStore} from 'pinia'

interface Menu {
  path: string
  name: string
  component: string
  meta: {
    title: string
    icon: string
    affix?: string
  }
}

const useAppStore = defineStore('app', {
  state: () => ({
    state: <boolean>false, // boolean
    message： <string>'msg', // string
    tagsView: <Menu[]>[] // array
  })
})
export default useAppStore

Answer 8

If the information isn't loading properly.

Check out:

Alternatively, you can try:

import {defineStore} from 'pinia'

interface Menu {
  path: string
  name: string
  component: string
  meta: {
    title: string
    icon: string
    affix?: string
  }
}

const useAppStore = defineStore('app', {
  state: () => ({
    state: <boolean>false, // boolean
    message： <string>'msg', // string
    tagsView: <Menu[]>[] // array
  })
})
export default useAppStore

Answer 9

Answer №5

Let's take a look at this illustration:

interface UserDetails {
  name: string
  age: number
}

const useUserInformation = defineStore<string, UserDetails>('user', {
  state: () => ({
    name: 'John Doe',
    age: 30,
  }),
})

Answer 10

Let's take a look at this illustration:

interface UserDetails {
  name: string
  age: number
}

const useUserInformation = defineStore<string, UserDetails>('user', {
  state: () => ({
    name: 'John Doe',
    age: 30,
  }),
})

Answer 11

Answer №6

Can you clarify the origin of the function getInitialBoard()? Is it being imported from another source? It's important to keep in mind that your initialized data should not be directly tied to your computed values. This responsibility falls more on the "getters" in pinia. In pinia, there are "state", "getters", and "actions". State typically consists of initialized, typed variables. Getters compute returnable values without modifying the state data. Actions are responsible for altering the state data. It's best practice to only modify the state data using store actions within pinia, rather than making changes directly within the component instance outside of pinia. Remember, all the data, which is considered the source of truth, should remain within pinia at all times. When structuring your stores, follow this organization:

// Example conceptual model
pinia {
  state: () => {
    return { data }
  },
  getters: { 
    // does not alter data
    getter: (state) => state.data.returnComputedState(),
  },
  actions: { 
    // modifies data
    action: () => this.data = mutateTheData(this.data),
  },
}

Answer 12

Can you clarify the origin of the function getInitialBoard()? Is it being imported from another source? It's important to keep in mind that your initialized data should not be directly tied to your computed values. This responsibility falls more on the "getters" in pinia. In pinia, there are "state", "getters", and "actions". State typically consists of initialized, typed variables. Getters compute returnable values without modifying the state data. Actions are responsible for altering the state data. It's best practice to only modify the state data using store actions within pinia, rather than making changes directly within the component instance outside of pinia. Remember, all the data, which is considered the source of truth, should remain within pinia at all times. When structuring your stores, follow this organization:

// Example conceptual model
pinia {
  state: () => {
    return { data }
  },
  getters: { 
    // does not alter data
    getter: (state) => state.data.returnComputedState(),
  },
  actions: { 
    // modifies data
    action: () => this.data = mutateTheData(this.data),
  },
}

What is the proper way to define the type of the state object in pinia?

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

Answer №6

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