Using String Enum to provide an index to an interface

Question

In Typescript I'd like to leverage my string enumeration:

export const enum MutationKeys {
    registerUser = 'registration/REGISTER',
    registerUserCompleted = 'registration/REGISTER_COMPLETED'
}

so that it's string values provide type-checking constraints on an object like this:

const mutations: IDictionary<VuexMutation> = {
    ['registration/REGISTER'](state, payload) {
        state.registration = {
            meta: {
                serverValidated: false
            },
            value: payload
        };
    },
    ['registration/REGISTER_COMPLETED'](state) {
        state.registration.meta.serverValidated = true;
    }
};

In the above example the IDictionary<VueMutation> interface allows me to type the value of the object vlue but allows any string index.

Jules Sam. Randolph · Accepted Answer · 2017-11-18 19:37:38Z

4

You can use key in construct :

export const enum MutationKeys {
  registerUser = 'registration/REGISTER',
  registerUserCompleted = 'registration/REGISTER_COMPLETED'
}

type MutationDictionnary<P> = {
  [key in MutationKeys]: P
}

const mutations: MutationDictionnary<VuexMutation> = {
  ['registration/REGISTER'](state, payload) {
    state.registration = {
      meta: {
        serverValidated: false
      },
      value: payload
    };
  },
  ['registration/REGISTER_COMPLETED'](state) {
    state.registration.meta.serverValidated = true;
  }
};

answered Nov 18, 2017 at 19:37

Jules Sam. Randolph

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