Question

我有下面的代码，我试图用对象数组中修改的几个属性来更新setState

onClick(index) {
    let tmp = this.state.daysOfWeek;
    tmp[index].active = !tmp[index].active;
    if (tmp[index].active === true) {
      tmp[index].className = "selectedDay";
    } else {
      tmp[index].className = "remSelectedDay";
    }

    this.setState({ daysOfWeek: [...this.state.daysOfWeek, tmp]})
  }

这里tmp是对象的修改数组。如果我使用传播运算符，则对象的携带将与tmp合并。

如何使用对象数组更新当前状态？

Answer 1

结合使用map和功能形式setState，可以在不直接修改状态的情况下正确更新数组：

onClick(index){
  this.setState(state => {
    return {
      daysOfWeek: state.daysOfWeek.map((day, i) => {
        if (i === index) {
          return {
            ...day,
            active: !day.active,
            className: day.active ? 'remSelectedDay' : 'selectedDay'
          }
        }
        return day;
      })
    }
  })
}

Answer 2

onClick (index) {
    const { daysOfWeek } = this.state        // for example: [1, 2, 3, 4, 5], index = 1
    this.setState({
        daysOfWeek: [
            ...daysOfWeek.slice(0, index),               // [1]
            {
                ...daysOfWeek[index],                    // this is 2
                active: !daysOfWeek[index],
                className: daysOfWeek[index] ? 'selectedDay' : 'remSelectedDay'
            },
            ...daysOfWeek.slice(index + 1)               // [3, 4, 5]
        ]
    })
}

反应setState更新对象数组

2 个答案: