CODEWITHSUNDEEP
reactjstypescript
Seth Killian
Seth Killian

Reputation: 963

TypeScript React State without Props

I'd like to take advantage of the static and strong typing in TypeScript, but only for the state since I don't intend to take in any props.

When I attempt to pass the interface as such, I end up with an error:

import * as React from 'react';
import {Link} from 'react-router-dom';
import Constants from '../Constants';

interface ILoginState {
   email: string;
   password: string;
   remember: boolean;
   error: string;
   isLoading: boolean;
}

class LoginView extends React.Component<{}, ILoginState> {

   constructor(props) {
      super(props);

      this.state = {
         email: '',
         password: '',
         remember: false,
         error: '',
         isLoading: false
      };
   }

 render() {
      return (<div>Login goes here</div>
      );
   }
}

export default LoginView;

I end up with a compile error:

ERROR in [at-loader] ./src/scripts/pages/LoginView.tsx:41:21 
    TS2345: Argument of type '{ [x: number]: any; }' is not assignable to parameter of type 'ILoginState | ((prevState: Readonly<ILoginState>, props: {}) => ILoginState | Pick<ILoginState, "...'.
  Type '{ [x: number]: any; }' is not assignable to type 'Pick<ILoginState, "email" | "password" | "remember" | "error" | "isLoading">'.
    Property 'email' is missing in type '{ [x: number]: any; }'.

I've also tried using 'any' in place of the empty brackets but that doesn't work either.

Here's the line 41 (this.SetState...) that the trace is referring to:

   handleChange = event => {
      const target = event.target;
      const value = target.type === 'checkbox' ? target.checked : target.value;
      this.setState({
         [target.name]: value
      });
   }

Here are all examples where that's used:

<input name="email" type="email" value={this.state.email} onChange={this.handleChange} />
<input name="password" type="password" value={this.state.password} onChange={this.handleChange} />
<input name="remember" type="checkbox" checked={this.state.remember} onChange={this.handleChange} />

Upvotes: 15

Views: 8497

Answers (2)

kevin Houguet Sysker
kevin Houguet Sysker

Reputation: 1

If you do not have props you can just do that :

export interface IMyClassState {
  menuItems: MenuItem[];
}

export default class MyClass extends Component <Record<string, never>, IMyClassState>{
  constructor(props = {}) {
      super(props);
      this.state = {
        menuItems: []
      } as IMyClassState;
    }
    
...

Upvotes: 0

yuval.bl
yuval.bl

Reputation: 5074

Option 1

class LoginView extends React.Component<{}, ILoginState> {
   constructor({}) {
   }
}

Option 2

class LoginView extends React.Component<null, ILoginState> {
   constructor(null) {
   }
}

Since props default value is an empty object, I personally prefer option 1.

Edit: it appears latest typescript versions do not support option 1. I'll suggest one of the following methods (tested on TS 3.7):

class LoginView extends React.Component<{}, ILoginState> {
   constructor() {
       super({});
   }
}

// OR
class LoginView extends React.Component<{}, ILoginState> {
   constructor(props = {}) {
       super(props);
   }
}

Thanks to @Andy who brought this update to my attention.

Upvotes: 12

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