接着看一下第二部分,调用stateMixin方法。
function stateMixin (Vue) {
// flow somehow has problems with directly declared definition object
// when using Object.defineProperty, so we have to procedurally build up
// the object here.
var dataDef = {};
dataDef.get = function () { return this._data };
var propsDef = {};
propsDef.get = function () { return this._props };
{
dataDef.set = function (newData) {
warn(
'Avoid replacing instance root $data. ' +
'Use nested data properties instead.',
this
);
};
propsDef.set = function () {
warn("$props is readonly.", this);
};
}
Object.defineProperty(Vue.prototype, '$data', dataDef);
Object.defineProperty(Vue.prototype, '$props', propsDef);
Vue.prototype.$set = set;
Vue.prototype.$delete = del;
Vue.prototype.$watch = function (
expOrFn,
cb,
options
) {
var vm = this;
options = options || {};
options.user = true;
var watcher = new Watcher(vm, expOrFn, cb, options);
if (options.immediate) {
cb.call(vm, watcher.value);
}
return function unwatchFn () {
watcher.teardown();
}
};
}
在Vue的原型上定义了几个属性,分别是$data、$props、$set、$delete、$watch。$data、$props
是实例的data和props的代理,可读不可写。
function set (target, key, val) {
if (Array.isArray(target) && typeof key === 'number') {
target.length = Math.max(target.length, key);
target.splice(key, 1, val);
return val
}
if (hasOwn(target, key)) {
target[key] = val;
return val
}
var ob = (target ).__ob__;
if (target._isVue || (ob && ob.vmCount)) {
"development" !== 'production' && warn(
'Avoid adding reactive properties to a Vue instance or its root $data ' +
'at runtime - declare it upfront in the data option.'
);
return val
}
if (!ob) {
target[key] = val;
return val
}
defineReactive$$1(ob.value, key, val);
ob.dep.notify();
return val
}
set方法为设置动态数据,接受Object和Array两种类型,可以对数组插入或者或替换操作,也可以替换已有的object的内容,如果不存在则新生成一个可变化的数据。
function del (target, key) {
if (Array.isArray(target) && typeof key === 'number') {
target.splice(key, 1);
return
}
var ob = (target ).__ob__;
if (target._isVue || (ob && ob.vmCount)) {
"development" !== 'production' && warn(
'Avoid deleting properties on a Vue instance or its root $data ' +
'- just set it to null.'
);
return
}
if (!hasOwn(target, key)) {
return
}
delete target[key];
if (!ob) {
return
}
ob.dep.notify();
}
delete方法删除数据中的动态参数,也接受Array和Object两种类型。
var Watcher = function Watcher (
vm,
expOrFn,
cb,
options
) {
this.vm = vm;
vm._watchers.push(this);
// options
if (options) {
this.deep = !!options.deep;
this.user = !!options.user;
this.lazy = !!options.lazy;
this.sync = !!options.sync;
} else {
this.deep = this.user = this.lazy = this.sync = false;
}
this.cb = cb;
this.id = ++uid$2; // uid for batching
this.active = true;
this.dirty = this.lazy; // for lazy watchers
this.deps = [];
this.newDeps = [];
this.depIds = new _Set();
this.newDepIds = new _Set();
this.expression = expOrFn.toString();
// parse expression for getter
if (typeof expOrFn === 'function') {
this.getter = expOrFn;
} else {
this.getter = parsePath(expOrFn);
if (!this.getter) {
this.getter = function () {};
"development" !== 'production' && warn(
"Failed watching path: \"" + expOrFn + "\" " +
'Watcher only accepts simple dot-delimited paths. ' +
'For full control, use a function instead.',
vm
);
}
}
this.value = this.lazy
? undefined
: this.get();
};
watch方法是观察某个属性或者某个计算属性的变化,第一个参数为观察的内容,第二个为回调函数,返回新值和旧值,第三个为属性配置。watch方法主要实例化了一个Watcher对象。
Watcher.prototype.get = function get () {
pushTarget(this);
var value;
var vm = this.vm;
if (this.user) {
try {
value = this.getter.call(vm, vm);
} catch (e) {
handleError(e, vm, ("getter for watcher \"" + (this.expression) + "\""));
}
} else {
value = this.getter.call(vm, vm);
}
// "touch" every property so they are all tracked as
// dependencies for deep watching
if (this.deep) {
traverse(value);
}
popTarget();
this.cleanupDeps();
return value
};
watcher原型的get方法,获取watcher方法所观察的值(this.getter.call(vm,vm))。
Watcher.prototype.addDep = function addDep (dep) {
var id = dep.id;
if (!this.newDepIds.has(id)) {
this.newDepIds.add(id);
this.newDeps.push(dep);
if (!this.depIds.has(id)) {
dep.addSub(this);
}
}
};
addDep方法,添加依赖。
Watcher.prototype.cleanupDeps = function cleanupDeps () {
var this$1 = this;
var i = this.deps.length;
while (i--) {
var dep = this$1.deps[i];
if (!this$1.newDepIds.has(dep.id)) {
dep.removeSub(this$1);
}
}
var tmp = this.depIds;
this.depIds = this.newDepIds;
this.newDepIds = tmp;
this.newDepIds.clear();
tmp = this.deps;
this.deps = this.newDeps;
this.newDeps = tmp;
this.newDeps.length = 0;
};
cleanupDeps方法,清除依赖。
Watcher.prototype.update = function update () {
/* istanbul ignore else */
if (this.lazy) {
this.dirty = true;
} else if (this.sync) {
this.run();
} else {
queueWatcher(this);
}
};
update方法,更新所观察的属性。
Watcher.prototype.run = function run () {
if (this.active) {
var value = this.get();
if (
value !== this.value ||
// Deep watchers and watchers on Object/Arrays should fire even
// when the value is the same, because the value may
// have mutated.
isObject(value) ||
this.deep
) {
// set new value
var oldValue = this.value;
this.value = value;
if (this.user) {
try {
this.cb.call(this.vm, value, oldValue);
} catch (e) {
handleError(e, this.vm, ("callback for watcher \"" + (this.expression) + "\""));
}
} else {
this.cb.call(this.vm, value, oldValue);
}
}
}
};
run方法,执行watcher实例所传的回调方法。
Watcher.prototype.evaluate = function evaluate () {
this.value = this.get();
this.dirty = false;
};
重新获取watcher内的value值。目前不是很理解。
Watcher.prototype.depend = function depend () {
var this$1 = this;
var i = this.deps.length;
while (i--) {
this$1.deps[i].depend();
}
};
为watcher内的每个dep添加依赖。
Watcher.prototype.teardown = function teardown () {
var this$1 = this;
if (this.active) {
// remove self from vm's watcher list
// this is a somewhat expensive operation so we skip it
// if the vm is being destroyed.
if (!this.vm._isBeingDestroyed) {
remove(this.vm._watchers, this);
}
var i = this.deps.length;
while (i--) {
this$1.deps[i].removeSub(this$1);
}
this.active = false;
}
};
移除watcher自身所绑定的依赖。