setState 与来自 onChange 的数组<select>避免改变</select> label

Question

TL;DR: calling this.setState to update an array avoid the change of a < select > label with the selected < option >

Explanations: I am building an array of options like that (dd is for drop down):

let ddUsers = (this.state.users.map(user => <option key={uuid.v4()} value={user.key}>{user.name}</option>))

Then here is my select:

<select onChange={this.handleFilter}>{ddUsers}</select>

This works perfectly: it appears first with the first option and is able to display the others.

Here is my onChange function: handleFilter

handleFilter = (event) => {

    let selectedUsers;

    console.log(event.target.value, this.state.DEFAULT_KEY)
    if (event.target.value === this.state.DEFAULT_KEY) {
        selectedUsers = [...this.state.users];
    } else {
        selectedUsers = (this.state.users.filter(user => user.key === event.target.value));
    }

    // this.setState({selected: selectedUsers}); <-- The problem comes from this line (looks like atleast)

}

Now with the commented last line, the label of the select correctly update to the selected options. But when I uncomment this line, the function is called, this.state.selected is updated BUT the select is blocked on the 1st option.

Is that clear? What am I missing?

In fact: just calling setState in the function avoid the correct change

Answer 1

This is because you are setting the key of option to dynamic value which gets updated every time. Try to use a know and unique one as the key . Code such as below

<option key={user.key} value={user.key}>

This ensures, you have unique key and also is predictable.