React-redux state array management

Question

So I basically started learning Redux and wanted to create a simple store app where you can add the phones to the cart. I have created a state object and within it, I have created an array with objects with a list of items in the store. I wanted to update on [+] click the number of items ordered but it doesn't work for now. I have been struggling with that for 1 hour already and still do not see where the problem might be.

Reducer looks like that:

const initialState = {
liked:0,
cart:0,
item: [
    {
        id:1,
        name: 'Iphone 8',
        price: 2000,
        desc: 'The new Iphone 8 available at our store!',
        orderedNum: 0
    },
    {
        id:2,
        name: 'Iphone 6',
        price: 1500,
        desc: 'The new Iphone 6 available at our store!',
        orderedNum: 0
    },
    {
        id:3,
        name: 'Samsung S8',
        price: 2200,
        desc: 'The new Samsung S8 available at our store!',
        orderedNum: 0
    },
    {
        id:4,
        name: 'Xiaomi Mi 6',
        price: 1400,
        desc: 'The new Xiaomi Mi 6 available at our store!',
        orderedNum: 0
    },
    {
        id:5,
        name: 'Pocophone P1',
        price: 2100,
        desc: 'The new Pocophone P1 available at our store!',
        orderedNum: 0
    },
    {
        id:6,
        name: 'Nokia 3310',
        price: 999,
        desc: 'The new Nokia 3310 available at our store!',
        orderedNum: 0
    },
]
}

const reducer = (state = initialState, action) => {
const newState = {...state};

switch(action.type) {
    case 'ADD_NUM':
        return state.item.map((el, index) => {
            if(el.id === action.id ){
                return {
                    ...el,
                    orderedNum: el.orderedNum + 1
                }
            }

            return el;
        })
    default:
        break;
}

return newState;
}

export default reducer;

• I have the action:

  const mapStateToProps = state => {
  return {
  item: state.item
  }
  }
  
  const mapDispatchToProps = dispatch => {
  return {
  addNum: () => dispatch ({
    type: 'ADD_NUM',
    id: this.props.id,
   value: 1
  })
  }
  

I have tried it in a different ways but I believe it could be the problem with nesting in the reducer.

Could someone advise?

Answer 1

Lets start with your reducer

const reducer = (state = initialState, action) => {
  switch (action.type) {
    case "ADD_NUM":
      return {
        // destruct and return a new object otherwise react wont update the UI
        ...state,
        item: state.item.map(el =>
          el.id === action.id
            ? { ...el , orderedNum: el.orderedNum + action.value }
            : el
        )
      };
    default:
      return state;
  }
};

mapDispatchToProps

const mapDispatchToProps = dispatch => {
  return {
    // add id to addNum
    addNum: id =>
      dispatch({
        type: "ADD_NUM",
        id,
        value: 1
      })
  };
};

Items component

const Items = ({ item, addNum }) => (
  item.map(el => (
    <div key={el.id}>
      <h1>{el.name}</h1>
      <h3>{el.price}</h3>
      <h3>{`orderedNum: ${el.orderedNum}`}</h3>
      // add the id to addNum
      <button onClick={() => addNum(el.id)}>+</button>
    </div>
  ))
);

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