How to update object in React state

问题:

I have an indexed list of users in the JS object (not array). It's part of the React state.

{
    1: { id: 1, name: "John" }
    2: { id: 2, name: "Jim" }
    3: { id: 3, name: "James" }
}

What's the best practice to:

1. add a new user { id: 4, name: "Jane" } with id (4) as key
2. remove a user with id 2
3. change the name of user #2 to "Peter"

Without any immutable helpers. I'm using Coffeescript and Underscore (so _.extend is ok...).

Thanks.

回答1:

This is what i would do

• add: var newUsers = _.extend({}, users, { 4: { id: 4, ... } })
• remove: var newUsers = _.extend({}, users) then delete newUsers['2']
• change: var newUsers = _.extend({}, users) then newUsers['2'].name = 'Peter'

回答2:

If you're not using Flux, you use this.setState() to update the state object.

delUser(id) {
    const users = this.state.users;
    delete users[id];
    this.setState(users);
}

addChangeUser(id, name) {
    const users = this.state.users;
    users[id] = {id: id, name: name};
    this.setState(users);
}

Then you can execute your test cases with this:

addChangeUser(4, 'Jane);
addChangeUser(2, 'Peter');
delUser(2);

回答3:

Apart from _.extend you can use Map for storing user

let user = new Map();
user.set(4, { id: 4, name: "Jane" }); //adds with id (4) as key
user.myMap.set(2, { id: 2, name: "Peter" }); // set user #2 to "Peter"
user.delete(3); //deletes user with id 3

回答4:

setState also accepts a function, which you might find more intuitive

function add( user ) {
  this.setState( users => {
    users[ user.id ] = user
    return users
  }
}

function remove( id ) {
  this.setState( users => {
    delete users[ id ]
    return users
}

These functions assume that your state object is your users object, if it is actually state.users then you'd have to pick users out, passing a function to setState will always be called passing the actual state object.

In this example add can also be used to amend, depending on your actual use-case you may want to create separate helpers.

回答5:

Using spreads:

Adding

this.setState({
  ...this.state,
  4: { id: 4, name: "Jane" },
}

Removing id 2

let prevState = this.state;
let {"2": id, ...nextState} = prevState;
this.setState({
  ...nextState,
}

Changing id 2

this.setState({
  ...this.state,
  2: {
    ...this.state["2"],
    name: "Peter",
  }
}