Vue.js计算属性不更新
Jar*_*mis 13 javascript single-page-application vue.js
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!
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语句打印出来的值是正确的,但是当我filteredClasses在模板中使用时,它只使用第一个缓存值并且永远不会更新模板.这是由Vue chrome devtools确认的(filteredClasses在初始缓存后永远不会改变).
谁能给我一些关于为什么会发生这种情况的信息？
Project.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>
So *_*Man 51
如果您的意图是计算属性在project.classes.someSubProperty更改时更新，则在定义计算属性时必须存在该子属性。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，这让我很头疼。我对状态的后续更改不会导致重新评估依赖于它的计算属性。向 Veux 状态添加具有空值的显式键解决了这个问题。
我不确定在您的情况下显式键是否可行，但它可能有助于解释计算属性过时的原因。
Vue reactiviy 文档，了解更多信息：https : //vuejs.org/v2/guide/reactivity.html#Change-Detection-Caveats
- 正如上面链接的文档所建议的，您可以使用 `this.$set(this.someObject, 'b', 2)`。 (4认同)
当值是undefined 时，我遇到了这个问题，然后计算无法检测到它的变化。我通过给它一个空的初始值来修复它。
根据Vue文档
- 这是对数据变量未能反应的正确解释，但不适用于计算属性，这就是这个问题的内容。 (5认同)
注意：请参阅下面我的更新，而不是使用此解决方法。
我有一个针对这种情况的解决方法，不知道你是否喜欢。我在下面放置了一个整数属性data()（我们称之为trigger），并且每当我在计算属性中使用的对象发生变化时，它就会增加 1。这样，每次对象发生变化时，计算属性都会更新。
例子：
export default {
data() {
return {
trigger: 0, // this will increment by 1 every time obj changes
obj: { x: 1 }, // the object used in computed property
};
},
computed: {
objComputed() {
// do anything with this.trigger. I'll log it to the console, just to be using it
console.log(this.trigger);
// thanks to this.trigger being used above, this line will work
return this.obj.y;
},
},
methods: {
updateObj() {
this.trigger += 1;
this.obj.y = true;
},
},
};
更新：在官方文档中找到了更好的方法，因此您不需要类似的东西this.trigger。
与上面的示例相同this.$set()：
export default {
data() {
return {
obj: { x: 1 }, // the object used in computed property
};
},
computed: {
objComputed() {
// note that `y` is not a property of `this.obj` initially
return this.obj.y;
},
},
methods: {
updateObj() {
// now the change will be detected
this.$set(this.obj, 'y', true);
},
},
};
这是一个链接
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