如何在Redux Reducer中的对象嵌套数组中添加项目

Question

Here is my example initial state:

let initialState = {
    data: {
        name: 'john',
          books: [
              {
                  name: 'a',
                  price: 220
              }
          ]
    }
}

How I can add new book item to books ?

I tried already

return {
        ...state,
        data :{
          ...state.data,
          books:{
              ...state.data.books,
              name : state.data.books.concat(action.payload.item.name),
              price : state.data.books.concat(action.payload.item.price)
          }
      }
      };

Any idea for that?

Important: I don't want to delete item which already in books I want to add new one with action payload

Answer 1

You missed some braces there, especially, books is array and you are inserting new object

return {
        ...state,
        data: {
          ...state.data,
          books: [
              ...state.data.books,
              {
                  name: action.payload.item.name,
                  price: action.payload.item.price
              }
          ]
      }
};

Answer 2

First of all, books is array. Second, if you want just to add a new item to the array, you can use array spread operator.

books: state.data.books.concat(action.payload.item) would also work.

return {
  ...state,
  data: {
    ...state.data,
    books: [
      ...state.data.books,
      action.payload.item
    ]
  }
};

Answer 3

Let's make our jobs easier by inventing tools of convenience -

 const update = (key, { [key]: value, ...state }, f) => ({ ...state, [key]: f (value) }) const initState = { data: { name: "john" , books: [ { name: "a", price: 20 } ] } } const payload = { item: { name: "b", price: 30 } } const nextState = update ('data', initState, x => update ('books', x, arr => [ ...arr, payload.item ] ) ) console.log(initState) console.log(nextState) 

Output

// initState
{ data:
    { name: "john"
    , books:
        [ { name: "a", price: 20 } ]
    }
}

// nextState
{ data:
    { name: "john"
    , books:
        [ { name: "a", price: 20 }
        , { name: "b", price: 30 }
        ]
    }
}

Answer 4

The answer is easy look at this

const book = {
            name : action.payload.item.name,
            price : action.payload.item.price
           };
return {
    ...state,
    data :{
      ...state.data,
      books: state.data.books.concat(book)              
      }      
};

you can find immutable update patterns here

Redux updated patterns