I don't understand why I'm getting this error:

Argument of type '{ id: string; }' is not assignable to parameter of type 'never'.

... at the line const index = state.sections.findIndex((section) => section.id === id);

in the following portion of my Vue store:

import { MutationTree, ActionTree, GetterTree } from 'vuex';

interface section {
  id: string;
  section_header: string;
  section_body: string;
  sectionItems: any;
}

interface sections extends Array<section>{}

export const state = () => ({
  sections: [
    {
      id: '1',
      section_header: 'lorem',
      sectionItems: []
    },
    {
      id: '2',
      section_header: 'ipsum',
      sectionItems: []
    }
  ]
});

type EditorState = ReturnType<typeof state>;

export const mutations: MutationTree<EditorState> = {
  ADD_SECTION_ITEM(state, id) {
    const index = state.sections.findIndex((section) => section.id === id);
    const sectionItem = {
      id: randomId()
    }
    state.sections[index].sectionItems.push(sectionItem);
  },
};

CodePudding user response：

I would say you probably need to type your sectionItems:

interface SectionItem {
  id: string
}

interface Section {
  id: string;
  section_header: string;
  section_body?: string;
  sectionItems: SectionItem;
}

Because, when you don't specify the type of sectionItems, typescript looks at the sectionItems that you initialised in your state (which are equal to []) and cannot identify the type of elements that should be in this array.

So you define it. Also, section_body should be optional because you it's not there in all your examples. Interface names should be capitalised in typescript.

Also, I do not think you need the sections interface. if you want to type something as an array of an interface, just use section[] as the type, like you would do string[].

Finally, this is up to you but I would advise against using different naming conventions in your interfaces (and in your code in general): section_body is snake_case and sectionItems is camelCase, it's usually better to stick to one and keep it in all the code.

CodePudding user response：

I think you need state.sections.push(sectionItem) instead of state.sections[index].sectionItems.push(sectionItems).