javascript – 使用……传播,但是redux仍然会对状态突变发出警告

Redux在发送时抛出警告：

Error: A state mutation was detected inside a dispatch,in the path: 
roundHistory.2.tickets. Take a look at the reducer(s) handling the action {"type":"ARCHIVE_TICKETS","roundId":"575acd8373e574282ef18717","data":[{"_id":"575acd9573e574282ef18718","value":7,"user_id":"574c72156f355fc723ecdbbf","round_id":"575acd8373e574282ef18717","__v":0},{"_id":"575acd9573e574282ef18719","value":9,{"_id":"575acd9573e574282ef1871a","value":8,{"_id":"575acdac73e574282ef1871b","value":19,{"_id":"575ad50c4c17851c12a3ec23","value":29,"user_id":"57522f0b1f08fc4257b9cbc6",{"_id":"575ad50c4c17851c12a3ec24","value":28,{"_id":"575ad

处理ARCHIVE_TICKETS动作的唯一减速器是这样的：

case 'ARCHIVE_TICKETS' :
  var archive = [...state.roundHistory];
  for (var i in archive) {
    if (archive[i]._id === action.roundId) {
      archive[i].tickets = action.data;
    }
  }
  return Object.assign({},state,{
    roundHistory: archive
  });

如果我使用[…传播],它怎么能改变状态呢？

解决方法

这里的[… state.roundHistory]类似于[] .concat(state.roundHistory).它正在创建一个新数组,但数组中的对象与state.roundHistory共享.如果你想改变它们,你需要复制每个项目.

您可以使用Object.assign执行此操作,类似于您为返回值执行的操作：

var archive = state.roundHistory.map(value => Object.assign({},value));

或者(正如您在自己的答案中所建议的那样),您可以使用对象扩展表示法：

var archive = state.roundHistory.map(value => {...value});