使用vue已經大半年時間了,寫起來已經很順手了。比起之前的jquery時代,vue配合webpack的使用,讓前端代碼整體性更強,代碼量也比之前少了一些。用了一段時間後,也想了解Vue具體是如何實現這樣的一個mvvm框架的,經過一段時間的掙扎,終於開始了源碼解析。ps:本次解讀的vue源碼版本爲2.3.3,本人水平有限,如果解析有誤的地方,請批評指正。
首先,不管採用什麼方式引入vue,直接script引入,requireJs引入等等等,vue都會進行相關的初始化工作。
function Vue$3 (options) {
if ("development" !== 'production' &&
!(this instanceof Vue$3)
) {
warn('Vue is a constructor and should be called with the `new` keyword');
}
this._init(options);
}
initMixin(Vue$3);
stateMixin(Vue$3);
eventsMixin(Vue$3);
lifecycleMixin(Vue$3);
renderMixin(Vue$3);
//全局Api的代碼在比較靠下的位置
initGlobalAPI(Vue$3);
定義了Vue$3這個類,接着調用了initMixin、stateMixin、eventsMixin、lifecycleMixin、renderMixin、initGlobalAPI幾個方法。
var uid$1 = 0;
function initMixin (Vue) {
Vue.prototype._init = function (options) {
var vm = this;
// a uid
vm._uid = uid$1++;
var startTag, endTag;
/* istanbul ignore if */
if ("development" !== 'production' && config.performance && mark) {
startTag = "vue-perf-init:" + (vm._uid);
endTag = "vue-perf-end:" + (vm._uid);
mark(startTag);
}
// a flag to avoid this being observed
vm._isVue = true;
// merge options
if (options && options._isComponent) {
// optimize internal component instantiation
// since dynamic options merging is pretty slow, and none of the
// internal component options needs special treatment.
initInternalComponent(vm, options);
} else {
vm.$options = mergeOptions(
resolveConstructorOptions(vm.constructor),
options || {},
vm
);
}
/* istanbul ignore else */
{
initProxy(vm);
}
// expose real self
vm._self = vm;
initLifecycle(vm);
initEvents(vm);
initRender(vm);
callHook(vm, 'beforeCreate');
initInjections(vm); // resolve injections before data/props
initState(vm);
initProvide(vm); // resolve provide after data/props
callHook(vm, 'created');
/* istanbul ignore if */
if ("development" !== 'production' && config.performance && mark) {
vm._name = formatComponentName(vm, false);
mark(endTag);
measure(((vm._name) + " init"), startTag, endTag);
}
if (vm.$options.el) {
vm.$mount(vm.$options.el);
}
};
}
initMixin方法,定義了Vue$3的_init的方法。startTag, endTag,mark爲開啓performance模式同時瀏覽器支持Performance.mark()方法時,在瀏覽器開發工具中對組件進行性能追蹤。根據_isComponent是否爲true調用initInternalComponent或mergeOptions進行options合併。
function initLifecycle (vm) {
var options = vm.$options;
// locate first non-abstract parent
var parent = options.parent;
if (parent && !options.abstract) {
while (parent.$options.abstract && parent.$parent) {
parent = parent.$parent;
}
parent.$children.push(vm);
}
vm.$parent = parent;
vm.$root = parent ? parent.$root : vm;
vm.$children = [];
vm.$refs = {};
vm._watcher = null;
vm._inactive = null;
vm._directInactive = false;
vm._isMounted = false;
vm._isDestroyed = false;
vm._isBeingDestroyed = false;
}
生命週期初始化,找到第一個非抽象parent,在$children數組中添加vm。$children
、$refs
等設置初始值。
function initEvents (vm) {
vm._events = Object.create(null);
vm._hasHookEvent = false;
// init parent attached events
var listeners = vm.$options._parentListeners;
if (listeners) {
updateComponentListeners(vm, listeners);
}
}
事件初始化,如果有父組件監聽調用updateComponentListeners更新監聽。
function initRender (vm) {
vm._vnode = null; // the root of the child tree
vm._staticTrees = null;
var parentVnode = vm.$vnode = vm.$options._parentVnode; // the placeholder node in parent tree
var renderContext = parentVnode && parentVnode.context;
vm.$slots = resolveSlots(vm.$options._renderChildren, renderContext);
vm.$scopedSlots = emptyObject;
// bind the createElement fn to this instance
// so that we get proper render context inside it.
// args order: tag, data, children, normalizationType, alwaysNormalize
// internal version is used by render functions compiled from templates
vm._c = function (a, b, c, d) { return createElement(vm, a, b, c, d, false); };
// normalization is always applied for the public version, used in
// user-written render functions.
vm.$createElement = function (a, b, c, d) { return createElement(vm, a, b, c, d, true); };
}
渲染初始化,調用resolveSlots方法返回vm子組件slots。渲染初始化結束後callHook(vm, ‘beforeCreate’)方法下發beforeCreate事件。
function initInjections (vm) {
var result = resolveInject(vm.$options.inject, vm);
if (result) {
Object.keys(result).forEach(function (key) {
/* istanbul ignore else */
{
defineReactive$$1(vm, key, result[key], function () {
warn(
"Avoid mutating an injected value directly since the changes will be " +
"overwritten whenever the provided component re-renders. " +
"injection being mutated: \"" + key + "\"",
vm
);
});
}
});
}
}
注入初始化。
function initState (vm) {
vm._watchers = [];
var opts = vm.$options;
if (opts.props) { initProps(vm, opts.props); }
if (opts.methods) { initMethods(vm, opts.methods); }
if (opts.data) {
initData(vm);
} else {
observe(vm._data = {}, true /* asRootData */);
}
if (opts.computed) { initComputed(vm, opts.computed); }
if (opts.watch) { initWatch(vm, opts.watch); }
}
初始化props、methods、data、computed、watch。
function initProvide (vm) {
var provide = vm.$options.provide;
if (provide) {
vm._provided = typeof provide === 'function'
? provide.call(vm)
: provide;
}
}
初始化provide。provide初始化結束後,調用callHook(vm, ‘created’)方法下發created事件。
if (vm.$options.el) {
vm.$mount(vm.$options.el);
}
最後,如果option中el存在,掛載元素到對應的el上,之後進行組件的渲染。