switch to vuepress

1 files changed, 240 insertions, 0 deletions

diff --git a/node_modules/vue/src/core/observer/watcher.js b/node_modules/vue/src/core/observer/watcher.js
new file mode 100644
index 00000000..48a2e612
--- /dev/null
+++ b/node_modules/vue/src/core/observer/watcher.js
@@ -0,0 +1,240 @@
+/* @flow */
+
+import {
+  warn,
+  remove,
+  isObject,
+  parsePath,
+  _Set as Set,
+  handleError
+} from '../util/index'
+
+import { traverse } from './traverse'
+import { queueWatcher } from './scheduler'
+import Dep, { pushTarget, popTarget } from './dep'
+
+import type { SimpleSet } from '../util/index'
+
+let uid = 0
+
+/**
+ * A watcher parses an expression, collects dependencies,
+ * and fires callback when the expression value changes.
+ * This is used for both the $watch() api and directives.
+ */
+export default class Watcher {
+  vm: Component;
+  expression: string;
+  cb: Function;
+  id: number;
+  deep: boolean;
+  user: boolean;
+  lazy: boolean;
+  sync: boolean;
+  dirty: boolean;
+  active: boolean;
+  deps: Array<Dep>;
+  newDeps: Array<Dep>;
+  depIds: SimpleSet;
+  newDepIds: SimpleSet;
+  getter: Function;
+  value: any;
+
+  constructor (
+    vm: Component,
+    expOrFn: string | Function,
+    cb: Function,
+    options?: ?Object,
+    isRenderWatcher?: boolean
+  ) {
+    this.vm = vm
+    if (isRenderWatcher) {
+      vm._watcher = this
+    }
+    vm._watchers.push(this)
+    // options
+    if (options) {
+      this.deep = !!options.deep
+      this.user = !!options.user
+      this.lazy = !!options.lazy
+      this.sync = !!options.sync
+    } else {
+      this.deep = this.user = this.lazy = this.sync = false
+    }
+    this.cb = cb
+    this.id = ++uid // uid for batching
+    this.active = true
+    this.dirty = this.lazy // for lazy watchers
+    this.deps = []
+    this.newDeps = []
+    this.depIds = new Set()
+    this.newDepIds = new Set()
+    this.expression = process.env.NODE_ENV !== 'production'
+      ? expOrFn.toString()
+      : ''
+    // parse expression for getter
+    if (typeof expOrFn === 'function') {
+      this.getter = expOrFn
+    } else {
+      this.getter = parsePath(expOrFn)
+      if (!this.getter) {
+        this.getter = function () {}
+        process.env.NODE_ENV !== 'production' && warn(
+          `Failed watching path: "${expOrFn}" ` +
+          'Watcher only accepts simple dot-delimited paths. ' +
+          'For full control, use a function instead.',
+          vm
+        )
+      }
+    }
+    this.value = this.lazy
+      ? undefined
+      : this.get()
+  }
+
+  /**
+   * Evaluate the getter, and re-collect dependencies.
+   */
+  get () {
+    pushTarget(this)
+    let value
+    const vm = this.vm
+    try {
+      value = this.getter.call(vm, vm)
+    } catch (e) {
+      if (this.user) {
+        handleError(e, vm, `getter for watcher "${this.expression}"`)
+      } else {
+        throw e
+      }
+    } finally {
+      // "touch" every property so they are all tracked as
+      // dependencies for deep watching
+      if (this.deep) {
+        traverse(value)
+      }
+      popTarget()
+      this.cleanupDeps()
+    }
+    return value
+  }
+
+  /**
+   * Add a dependency to this directive.
+   */
+  addDep (dep: Dep) {
+    const id = dep.id
+    if (!this.newDepIds.has(id)) {
+      this.newDepIds.add(id)
+      this.newDeps.push(dep)
+      if (!this.depIds.has(id)) {
+        dep.addSub(this)
+      }
+    }
+  }
+
+  /**
+   * Clean up for dependency collection.
+   */
+  cleanupDeps () {
+    let i = this.deps.length
+    while (i--) {
+      const dep = this.deps[i]
+      if (!this.newDepIds.has(dep.id)) {
+        dep.removeSub(this)
+      }
+    }
+    let 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
+  }
+
+  /**
+   * Subscriber interface.
+   * Will be called when a dependency changes.
+   */
+  update () {
+    /* istanbul ignore else */
+    if (this.lazy) {
+      this.dirty = true
+    } else if (this.sync) {
+      this.run()
+    } else {
+      queueWatcher(this)
+    }
+  }
+
+  /**
+   * Scheduler job interface.
+   * Will be called by the scheduler.
+   */
+  run () {
+    if (this.active) {
+      const 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
+        const 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)
+        }
+      }
+    }
+  }
+
+  /**
+   * Evaluate the value of the watcher.
+   * This only gets called for lazy watchers.
+   */
+  evaluate () {
+    this.value = this.get()
+    this.dirty = false
+  }
+
+  /**
+   * Depend on all deps collected by this watcher.
+   */
+  depend () {
+    let i = this.deps.length
+    while (i--) {
+      this.deps[i].depend()
+    }
+  }
+
+  /**
+   * Remove self from all dependencies' subscriber list.
+   */
+  teardown () {
+    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)
+      }
+      let i = this.deps.length
+      while (i--) {
+        this.deps[i].removeSub(this)
+      }
+      this.active = false
+    }
+  }
+}