Using TypeScript to specify data types in the Vue data object

Question

Using TypeScript to specify data types in the Vue data object

I am currently utilizing Vue.js with Typescript in a webpack project.

Following the guidelines provided in the Recommended Configuration in my tsconfig.json, I have set:

"strict": true,

Within one of my components, I have:

declare interface Player {
    cod: string,
    param: string
  }

export default Vue.extend({
    name: 'basecomponent',
    data() {
      return {
        players: []
      };
    },
    created() 
      let self = this
      axios.get('fetch-data')
        .then((response) => {
          let res: Players[] = response.data;
          for(let i = 0; i < res.length; i++){
              self.players.push(res[i]);
          }
        })
        .catch((error: string) => {
          console.log(error);
       });
    },
 });

However, when attempting to compile, I encounter the following error:

 error TS2345: Argument of type 'Player' is not assignable to parameter of type 'never'.

I suspect that players: [] has the type never[].

My inquiry is: How can I determine the types for Vue data object properties?

typescript vue.js vuejs2

Answer 1

Answer №1

Expanding on the response from Joshua, it is advisable to specify the type of players within the code directly to prevent it from becoming overly verbose as your dataset grows in size.

data() {
  return {
    members: [] as Member[]
  };
},

Alternatively:

data() {
  return {
    participants: new Array<Player>()
  };
},

Answer 2

Expanding on the response from Joshua, it is advisable to specify the type of players within the code directly to prevent it from becoming overly verbose as your dataset grows in size.

data() {
  return {
    members: [] as Member[]
  };
},

Alternatively:

data() {
  return {
    participants: new Array<Player>()
  };
},

Answer 3

Answer №2

Here is an example that should function as intended:

interface User {
  id: number,
  name: string
}

interface UserData {
  users: User[]
}

export default Vue.extend({
  name: 'usercomponent',
  data(): UserData {
    return {
      users: []
    };
  },
})

Answer 4

Here is an example that should function as intended:

interface User {
  id: number,
  name: string
}

interface UserData {
  users: User[]
}

export default Vue.extend({
  name: 'usercomponent',
  data(): UserData {
    return {
      users: []
    };
  },
})

Answer 5

Answer №3

Make sure to declare a return value in your data method.

This will help TypeScript understand the expected type for the players property.

Simply update the data() { line with the following:

data() : {
  players: Array<any>, // Consider using a more specific type instead of `any`
} {
  return {
    players: []
  };
},

By making this change, the players property will be correctly typed as an Array of any.

Answer 6

Make sure to declare a return value in your data method.

This will help TypeScript understand the expected type for the players property.

Simply update the data() { line with the following:

data() : {
  players: Array<any>, // Consider using a more specific type instead of `any`
} {
  return {
    players: []
  };
},

By making this change, the players property will be correctly typed as an Array of any.

Answer 7

Answer №4

Discovering an alternative approach that closely resembles the traditional syntax, yet maintains concise code.

data() {
  return new function {
    members: Member[] = []
   }();
},

Answer 8

Discovering an alternative approach that closely resembles the traditional syntax, yet maintains concise code.

data() {
  return new function {
    members: Member[] = []
   }();
},

Answer 9

Answer №5

The use of the '<>' syntax for type assertion is prohibited. Instead, please utilize the 'as' syntax as shown below:

Here is a visual representation:

teams: [] as Team[]

Answer 10

The use of the '<>' syntax for type assertion is prohibited. Instead, please utilize the 'as' syntax as shown below:

Here is a visual representation:

teams: [] as Team[]

Answer 11

Answer №6

If anyone happens upon this in the future, here is the solution that resolved my issue. It may be a bit more verbose, but it ensures proper type inference throughout the Vue.extend() component definition:

interface Player {
  cod: string,
  param: string
}

// Include any properties defined in the `data()` return object here.
interface Data {
  players: Player[];
}

// Include any methods defined in "methods()" here.
interface Methods {}

// Include any computed properties from "computed()" here.
interface Computed {}

// Declare any component props here.
interface Props {}

export default Vue.extend<Data, Methods, Computed, Props>({
    name: 'basecomponent',
    data() {
      return {
        players: []
      };
    },
    // It's recommended to switch to the "mounted()" component lifecycle, as issues can occur when modifying data within "created()".
    created() {
      // The following lines are optional.
      // let self = this
      // By typing the Axios.get() method like this, the .data property is automatically typed.
      axios.get<Players[]>('fetch-data')
        .then(({ data }) => {
          // The next lines are optional.
          // let res: Players[] = response.data;
          // for(let i = 0; i < data.length; i++){
          //     self.players.push(data[i]);
          // }
          this.players = data;
        })
        .catch((error: string) => {
          console.log(error);
       });
    },
 });

Answer 12

If anyone happens upon this in the future, here is the solution that resolved my issue. It may be a bit more verbose, but it ensures proper type inference throughout the Vue.extend() component definition:

interface Player {
  cod: string,
  param: string
}

// Include any properties defined in the `data()` return object here.
interface Data {
  players: Player[];
}

// Include any methods defined in "methods()" here.
interface Methods {}

// Include any computed properties from "computed()" here.
interface Computed {}

// Declare any component props here.
interface Props {}

export default Vue.extend<Data, Methods, Computed, Props>({
    name: 'basecomponent',
    data() {
      return {
        players: []
      };
    },
    // It's recommended to switch to the "mounted()" component lifecycle, as issues can occur when modifying data within "created()".
    created() {
      // The following lines are optional.
      // let self = this
      // By typing the Axios.get() method like this, the .data property is automatically typed.
      axios.get<Players[]>('fetch-data')
        .then(({ data }) => {
          // The next lines are optional.
          // let res: Players[] = response.data;
          // for(let i = 0; i < data.length; i++){
          //     self.players.push(data[i]);
          // }
          this.players = data;
        })
        .catch((error: string) => {
          console.log(error);
       });
    },
 });

Answer 13

Answer №7

In order to avoid detailing the entire data structure, it may be more practical to start by explicitly defining players as a variable with a specified type:

export default Vue.extend({
    name: 'basecomponent',
    data() {
      const players: Player[] = [];
      return {
        players: players
      };
    },
...

This approach should also apply to other intricate types, not limited to arrays. However, I am still figuring out how to prevent volar from restricting the union type based on the initializer value -_-

Answer 14

In order to avoid detailing the entire data structure, it may be more practical to start by explicitly defining players as a variable with a specified type:

export default Vue.extend({
    name: 'basecomponent',
    data() {
      const players: Player[] = [];
      return {
        players: players
      };
    },
...

This approach should also apply to other intricate types, not limited to arrays. However, I am still figuring out how to prevent volar from restricting the union type based on the initializer value -_-

Using TypeScript to specify data types in the Vue data object

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

Answer №6

Answer №7

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