javascript - Vue.js 计算属性不更新

Question

我正在使用 Vue.js 计算属性，但遇到了一个问题:计算方法 IS 在正确的时间被调用，但计算方法返回的值被忽略了!

我的方法

computed: {
    filteredClasses() {
        let classes = this.project.classes
        const ret = classes && classes.map(klass => {
            const klassRet = Object.assign({}, klass)
            klassRet.methods = klass.methods.filter(meth => this.isFiltered(meth, klass))
            return klassRet
        })
        console.log(JSON.stringify(ret))
        return ret
    }
}

console.log 语句打印出的值是正确的，但是当我在模板中使用 filteredClasses 时，它只使用第一个缓存值 并且从不更新模板。 Vue chrome devtools 证实了这一点(filteredClasses 在初始缓存后永远不会改变)。

谁能告诉我一些信息，说明为什么会这样？

项目.vue

<template>
<div>
    <div class="card light-blue white-text">
        <div class="card-content row">
            <div class="col s4 input-field-white inline">
                <input type="text" v-model="filter.name" id="filter-name">
                <label for="filter-name">Name</label>
            </div>
            <div class="col s2 input-field-white inline">
                <input type="text" v-model="filter.status" id="filter-status">
                <label for="filter-status">Status (PASS or FAIL)</label>
            </div>
            <div class="col s2 input-field-white inline">
                <input type="text" v-model="filter.apkVersion" id="filter-apkVersion">
                <label for="filter-apkVersion">APK Version</label>
            </div>
            <div class="col s4 input-field-white inline">
                <input type="text" v-model="filter.executionStatus" id="filter-executionStatus">
                <label for="filter-executionStatus">Execution Status (RUNNING, QUEUED, or IDLE)</label>
            </div>
        </div>
    </div>
    <div v-for="(klass, classIndex) in filteredClasses">
        <ClassView :klass-raw="klass"/>
    </div>
</div>
</template>

<script>
import ClassView from "./ClassView.vue"

export default {
    name: "ProjectView",

    props: {
        projectId: {
            type: String,
            default() {
                return this.$route.params.id
            }
        }
    },

    data() {
        return {
            project: {},
            filter: {
                name: "",
                status: "",
                apkVersion: "",
                executionStatus: ""
            }
        }
    },

    async created() {
        // Get initial data
        const res = await this.$lokka.query(`{
            project(id: "${this.projectId}") {
                name
                classes {
                    name
                    methods {
                        id
                        name
                        reports
                        executionStatus
                    }
                }
            }
        }`)

        // Augment this data with latestReport and expanded
        const reportPromises = []
        const reportMeta     = []
        for(let i = 0; i < res.project.classes.length; ++i) {
           const klass = res.project.classes[i];
           for(let j = 0; j < klass.methods.length; ++j) {
               res.project.classes[i].methods[j].expanded = false
               const meth = klass.methods[j]
               if(meth.reports && meth.reports.length) {
                   reportPromises.push(
                       this.$lokka.query(`{
                           report(id: "${meth.reports[meth.reports.length-1]}") {
                               id
                               status
                               apkVersion
                               steps {
                                   status platform message time
                               }
                           }
                       }`)
                       .then(res => res.report)
                    )
                    reportMeta.push({
                        classIndex: i,
                        methodIndex: j
                    })
                }
            }
        }

        // Send all report requests in parallel
        const reports = await Promise.all(reportPromises)

        for(let i = 0; i < reports.length; ++i) {
           const {classIndex, methodIndex} = reportMeta[i]
           res.project.classes[classIndex]
                      .methods[methodIndex]
                      .latestReport = reports[i]
       }

       this.project = res.project

       // Establish WebSocket connection and set up event handlers
       this.registerExecutorSocket()
   },

   computed: {
       filteredClasses() {
           let classes = this.project.classes
           const ret = classes && classes.map(klass => {
                const klassRet = Object.assign({}, klass)
                klassRet.methods = klass.methods.filter(meth => this.isFiltered(meth, klass))
                return klassRet
            })
            console.log(JSON.stringify(ret))
            return ret
        }
    },

    methods: {
        isFiltered(method, klass) {
            const nameFilter = this.testFilter(
                this.filter.name,
                klass.name + "." + method.name
            )
            const statusFilter = this.testFilter(
                this.filter.status,
                method.latestReport && method.latestReport.status
           )
           const apkVersionFilter = this.testFilter(
               this.filter.apkVersion,
               method.latestReport && method.latestReport.apkVersion
           )
           const executionStatusFilter = this.testFilter(
               this.filter.executionStatus,
               method.executionStatus
           )
           return nameFilter && statusFilter && apkVersionFilter && executionStatusFilter
       },
       testFilter(filter, item) {
           item = item || ""
           let outerRet = !filter ||
           // Split on '&' operator
           filter.toLowerCase().split("&").map(x => x.trim()).map(seg =>
               // Split on '|' operator
               seg.split("|").map(x => x.trim()).map(segment => {
                   let quoted = false, postOp = x => x
                   // Check for negation
                   if(segment.indexOf("!") === 0) {
                       if(segment.length > 1) {
                           segment = segment.slice(1, segment.length)
                           postOp = x => !x
                       }
                   }
                   // Check for quoted
                   if(segment.indexOf("'") === 0 || segment.indexOf("\"") === 0) {
                       if(segment[segment.length-1] === segment[0]) {
                           segment = segment.slice(1, segment.length-1)
                           quoted = true
                       }
                   }
                   if(!quoted || segment !== "") {
                       //console.log(`Item: ${item}, Segment: ${segment}`)
                       //console.log(`Result: ${item.toLowerCase().includes(segment)}`)
                       //console.log(`Result': ${postOp(item.toLowerCase().includes(segment))}`)
                   }
                   let innerRet = quoted && segment === "" ?
                       postOp(!item) :
                       postOp(item.toLowerCase().includes(segment))

                   //console.log(`InnerRet(${filter}, ${item}): ${innerRet}`)

                   return innerRet
               }).reduce((x, y) => x || y, false)
           ).reduce((x, y) => x && y, true)

           //console.log(`OuterRet(${filter}, ${item}): ${outerRet}`)
           return outerRet
       },
       execute(methID, klassI, methI) {
           this.project.classes[klassI].methods[methI].executionStatus = "QUEUED"
           // Make HTTP request to execute method
           this.$http.post("/api/Method/" + methID + "/Execute")
           .then(response => {
           }, error =>
               console.log("Couldn't execute Test: " + JSON.stringify(error))
           )
       },
       registerExecutorSocket() {
           const socket = new WebSocket("ws://localhost:4567/api/Executor/")

           socket.onmessage = msg => {
               const {methodID, report, executionStatus} = JSON.parse(msg.data)

               for(let i = 0; i < this.project.classes.length; ++i) {
                   const klass = this.project.classes[i]
                   for(let j = 0; j < klass.methods.length; ++j) {
                       const meth = klass.methods[j]
                       if(meth.id === methodID) {
                           if(report)
                               this.project.classes[i].methods[j].latestReport = report
                           if(executionStatus)
                               this.project.classes[i].methods[j].executionStatus = executionStatus
                           return
                       }
                   }
               }
           }
       },
       prettyName: function(name) {
           const split = name.split(".")
           return split[split.length-1]
       }
   },

   components: {
       "ClassView": ClassView
   }
}
</script>

<style scoped>
</style>

Answer 1

如果您打算在 project.classes.someSubProperty 更改时更新计算属性，则在定义计算属性时该子属性必须存在。 Vue 无法检测属性的添加或删除，只能检测对现有属性的更改。

当使用带有空 state 对象的 Vuex 存储时，这让我很困扰。我对状态的后续更改不会导致依赖于它被重新评估的计算属性。向 Veux 状态添加具有空值的显式键解决了这个问题。

我不确定显式键在您的情况下是否可行，但这可能有助于解释为什么计算属性会过时。

Vue 响应式文档，了解更多信息: https://v2.vuejs.org/v2/guide/reactivity.html#Change-Detection-Caveats