vue 项目中需要在子组件中动态接收父组件传递的事件名来监听，直接用 v-on 或者 @ 符号加上中括号[]动态绑定事件名是可以实现的，一个简单的 demo 如下：
<template>
<!-- <div v-on:[eventName]="handleEvent">动态事件</div> -->
<div @[eventName]="handleEvent">动态事件</div>
</template>
<script>
export default {
data() {
return {
eventName: 'click',
}
},
methods: {
handleEvent(e) {
console.log(e)
}
}
}
</script>
之前在 iview 的一个项目中这样使用是没问题的，换到 element-ui 的项目中发现上面的写法就是不生效，开始还以为是 UI 框架的问题，最后不断切换 vue 的版本才发现了问题的根源。
不生效的 element-ui 项目中 vue 版本是 2.5.2，生效的 iview 项目中 vue 版本是 2.6.7，不断切换 vue 版本才发现需要 2.6.0 以上版本才支持动态绑定事件名。
最终在 vue 官方的版本更新日志里也找到了答案：v2.6.0-beta.2 - support dynamic directive arguments for v-on, v-bind and custom directives，v2.6.0-beta.2版本才开始支持动态绑定事件名和属性名。
翻看 vue 2.6 版本的源码，找到的几个相关的方法：
processAttrs 方法
// vue\src\compiler\parser\index.js
function processAttrs (el) {
const list = el.attrsList
let i, l, name, rawName, value, modifiers, syncGen, isDynamic
for (i = 0, l = list.length; i < l; i++) {
name = rawName = list[i].name
value = list[i].value
if (dirRE.test(name)) {
// mark element as dynamic
el.hasBindings = true
// modifiers
modifiers = parseModifiers(name.replace(dirRE, ''))
// support .foo shorthand syntax for the .prop modifier
if (process.env.VBIND_PROP_SHORTHAND && propBindRE.test(name)) {
(modifiers || (modifiers = {
})).prop = true
name = `.` + name.slice(1).replace(modifierRE, '')
} else if (modifiers) {
name = name.replace(modifierRE, '')
}
if (bindRE.test(name)) {
// v-bind
name = name.replace(bindRE, '')
value = parseFilters(value)
isDynamic = dynamicArgRE.test(name)
if (isDynamic) {
name = name.slice(1, -1)
}
if (
process.env.NODE_ENV !== 'production' &&
value.trim().length === 0
) {
warn(
`The value for a v-bind expression cannot be empty. Found in "v-bind:${
name}"`
)
}
if (modifiers) {
if (modifiers.prop && !isDynamic) {
name = camelize(name)
if (name === 'innerHtml') name = 'innerHTML'
}
if (modifiers.camel && !isDynamic) {
name = camelize(name)
}
if (modifiers.sync) {
syncGen = genAssignmentCode(value, `$event`)
if (!isDynamic) {
addHandler(
el,
`update:${
camelize(name)}`,
syncGen,
null,
false,
warn,
list[i]
)
if (hyphenate(name) !== camelize(name)) {
addHandler(
el,
`update:${
hyphenate(name)}`,
syncGen,
null,
false,
warn,
list[i]
)
}
} else {
// handler w/ dynamic event name
addHandler(
el,
`"update:"+(${
name})`,
syncGen,
null,
false,
warn,
list[i],
true // dynamic
)
}
}
}
if ((modifiers && modifiers.prop) || (
!el.component && platformMustUseProp(el.tag, el.attrsMap.type, name)
)) {
addProp(el, name, value, list[i], isDynamic)
} else {
addAttr(el, name, value, list[i], isDynamic)
}
} else if (onRE.test(name)) {
// v-on
name = name.replace(onRE, '')
isDynamic = dynamicArgRE.test(name)
if (isDynamic) {
name = name.slice(1, -1)
}
addHandler(el, name, value, modifiers, false, warn, list[i], isDynamic)
} else {
// normal directives
name = name.replace(dirRE, '')
// parse arg
const argMatch = name.match(argRE)
let arg = argMatch && argMatch[1]
isDynamic = false
if (arg) {
name = name.slice(0, -(arg.length + 1))
if (dynamicArgRE.test(arg)) {
arg = arg.slice(1, -1)
isDynamic = true
}
}
addDirective(el, name, rawName, value, arg, isDynamic, modifiers, list[i])
if (process.env.NODE_ENV !== 'production' && name === 'model') {
checkForAliasModel(el, value)
}
}
} else {
// literal attribute
if (process.env.NODE_ENV !== 'production') {
const res = parseText(value, delimiters)
if (res) {
warn(
`${
name}="${
value}": ` +
'Interpolation inside attributes has been removed. ' +
'Use v-bind or the colon shorthand instead. For example, ' +
'instead of <div id="{
{ val }}">, use <div :id="val">.',
list[i]
)
}
}
addAttr(el, name, JSON.stringify(value), list[i])
// #6887 firefox doesn't update muted state if set via attribute
// even immediately after element creation
if (!el.component &&
name === 'muted' &&
platformMustUseProp(el.tag, el.attrsMap.type, name)) {
addProp(el, name, 'true', list[i])
}
}
}
}
addHandler 方法
// vue\src\compiler\helpers.js
export function addHandler (
el: ASTElement,
name: string,
value: string,
modifiers: ?ASTModifiers,
important?: boolean,
warn?: ?Function,
range?: Range,
dynamic?: boolean
) {
modifiers = modifiers || emptyObject
// warn prevent and passive modifier
/* istanbul ignore if */
if (
process.env.NODE_ENV !== 'production' && warn &&
modifiers.prevent && modifiers.passive
) {
warn(
'passive and prevent can\'t be used together. ' +
'Passive handler can\'t prevent default event.',
range
)
}
// normalize click.right and click.middle since they don't actually fire
// this is technically browser-specific, but at least for now browsers are
// the only target envs that have right/middle clicks.
if (modifiers.right) {
if (dynamic) {
name = `(${
name})==='click'?'contextmenu':(${
name})`
} else if (name === 'click') {
name = 'contextmenu'
delete modifiers.right
}
} else if (modifiers.middle) {
if (dynamic) {
name = `(${
name})==='click'?'mouseup':(${
name})`
} else if (name === 'click') {
name = 'mouseup'
}
}
// check capture modifier
if (modifiers.capture) {
delete modifiers.capture
name = prependModifierMarker('!', name, dynamic)
}
if (modifiers.once) {
delete modifiers.once
name = prependModifierMarker('~', name, dynamic)
}
/* istanbul ignore if */
if (modifiers.passive) {
delete modifiers.passive
name = prependModifierMarker('&', name, dynamic)
}
let events
if (modifiers.native) {
delete modifiers.native
events = el.nativeEvents || (el.nativeEvents = {
})
} else {
events = el.events || (el.events = {
})
}
const newHandler: any = rangeSetItem({
value: value.trim(), dynamic }, range)
if (modifiers !== emptyObject) {
newHandler.modifiers = modifiers
}
const handlers = events[name]
/* istanbul ignore if */
if (Array.isArray(handlers)) {
important ? handlers.unshift(newHandler) : handlers.push(newHandler)
} else if (handlers) {
events[name] = important ? [newHandler, handlers] : [handlers, newHandler]
} else {
events[name] = newHandler
}
el.plain = false
}
genHandlers 方法
// vue\src\compiler\codegen\events.js
export function genHandlers (
events: ASTElementHandlers,
isNative: boolean
): string {
const prefix = isNative ? 'nativeOn:' : 'on:'
let staticHandlers = ``
let dynamicHandlers = ``
for (const name in events) {
const handlerCode = genHandler(events[name])
if (events[name] && events[name].dynamic) {
dynamicHandlers += `${
name},${
handlerCode},`
} else {
staticHandlers += `"${
name}":${
handlerCode},`
}
}
staticHandlers = `{
${
staticHandlers.slice(0, -1)}}`
if (dynamicHandlers) {
return prefix + `_d(${
staticHandlers},[${
dynamicHandlers.slice(0, -1)}])`
} else {
return prefix + staticHandlers
}
}
