当一项有一些更改时更新vuex数组的状态

Question

我的vuex商店中有一个名为case的数组。

当我更新数组中现有项目中的几个字段时，我想用新内容更新数组。

我以为我可以在变异中做类似的事情，但无法正常工作并得到错误typeError: undefined is not an object (evaluating 'state.objects.find')-

EDIT_CASE (state, payload) {
    const item = state.objects.find(item => item.id === payload.recordId);
Object.assign(item, payload.case_status);

我的数组如下：

[
    {
        "case_name": "Laptop not working",
        "case_status": "live",
        "case_summary": "This is some summary content",
        "createdBy": "zippy",
        "createdDate": "2018-06-21T15:20:22.932Z",
        "id": "-LFXvk9yY5c-O8yIdf8k"
    },
    {
        "case_name": "Something else",
        "case_status": "live",
        "case_summary": "This is some summary content",
        "createdBy": "zippy",
        "createdDate": "2018-06-21T15:20:22.932Z",
        "id": "-STVvk9yY5c-O3yiTy8k"
    }
]

我还认为，根据我所读的内容，Vue不会观察到数组内的变化，因此这可能是我走错了路，需要删除然后重新添加数组项吗？

基本上，我有一个列表，我对后端进行了更改，现在我希望该列表反映我通过更新案例状态所做的更改，任何人都可以帮忙吗？

Answer 1

您的示例没有数组问题，因为您尝试更改对象属性-而不是数组元素引用。问题出在Object.assign(item, payload.case_status);-您应该提供一个对象而不仅仅是一个字段。（您还说过，名为casesexample的数组具有objects，也许这也是个问题）；

所以这应该工作：

EDIT_CASE (state, payload) {
    const item = state.objects.find(item => item.id === payload.recordId);
    Object.assign(item, payload);
}

错误：

未定义不是对象

我认为，这与之相关，Object.assign因为您将字段传递给了未定义的字段。

PS有一个小例子可以帮助您了解何时出现阵列问题以及何时一切正常。查看代码注释：）

EDIT_CASE (state, payload) {
    const item = state.objects.find(item => item.id === payload.recordId);
    Object.assign(item, payload);
}

new Vue({
  el: "#app",
  data: {
    todos: [
      { text: "Learn JavaScript" },
      { text: "Learn Vue" },
      { text: "Play around in JSFiddle" },
      { text: "Build something awesome" }
    ]
  },
  methods: {
    // work because object property is reactive
  	changeItemProperty() {
    	this.todos[3].text = "changedItemProperty";
    },
    // same reason, properties are reactive
    changeItemWithAssign() {
    	Object.assign(this.todos[3], { text: "changedItemWithAssign" });
    },
    // does not work, can not track changes in array
    // also this will break all attempts to change TEXT property in UI
    // because property becomes not reactive after this due to new object
    // try to changeItemProperty or  changeItemWithAssign - does not work!
    // changeItem2 will fix it :)
    changeItem() {
    	this.todos[3] = { text: "changedItem" }
    },
    // works
    changeItem2() {
    	Vue.set(this.todos, 3, { text: "changedItem2" });
    }	
  }
})

Answer 2

JavaScript（不是Vue特有的）无法检测直接通过索引设置Array项的值arr[3] = 'stop'; ，也无法检测从对象添加新键或删除现有键。您必须定义商店的初始状态，例如

const store = new Vuex.Store({
  state: {
    objects: []
  },
  mutations: {
    EDIT_CASE (state, payload) {
      const index = state.objects.findIndex(item => item.id === payload.id);
      if (index !== -1) state.objects.splice(index, 1, payload);
    }
  }
})