binding.js

var Batcher        = require('./batcher'),
    bindingBatcher = new Batcher(),
    bindingId      = 1

/**
 *  Binding class.
 *
 *  each property on the viewmodel has one corresponding Binding object
 *  which has multiple directive instances on the DOM
 *  and multiple computed property dependents
 */
function Binding (compiler, key, isExp, isFn) {
    this.id = bindingId++
    this.value = undefined
    this.isExp = !!isExp
    this.isFn = isFn
    this.root = !this.isExp && key.indexOf('.') === -1
    this.compiler = compiler
    this.key = key
    this.dirs = []
    this.subs = []
    this.deps = []
    this.unbound = false
}

var BindingProto = Binding.prototype

/**
 *  Update value and queue instance updates.
 */
BindingProto.update = function (value) {
    if (!this.isComputed || this.isFn) {
        this.value = value
    }
    if (this.dirs.length || this.subs.length) {
        var self = this
        bindingBatcher.push({
            id: this.id,
            execute: function () {
                if (!self.unbound) {
                    self._update()
                }
            }
        })
    }
}

/**
 *  Actually update the directives.
 */
BindingProto._update = function () {
    var i = this.dirs.length,
        value = this.val()
    while (i--) {
        this.dirs[i].$update(value)
    }
    this.pub()
}

/**
 *  Return the valuated value regardless
 *  of whether it is computed or not
 */
BindingProto.val = function () {
    return this.isComputed && !this.isFn
        ? this.value.$get()
        : this.value
}

/**
 *  Notify computed properties that depend on this binding
 *  to update themselves
 */
BindingProto.pub = function () {
    var i = this.subs.length
    while (i--) {
        this.subs[i].update()
    }
}

/**
 *  Unbind the binding, remove itself from all of its dependencies
 */
BindingProto.unbind = function () {
    // Indicate this has been unbound.
    // It's possible this binding will be in
    // the batcher's flush queue when its owner
    // compiler has already been destroyed.
    this.unbound = true
    var i = this.dirs.length
    while (i--) {
        this.dirs[i].$unbind()
    }
    i = this.deps.length
    var subs
    while (i--) {
        subs = this.deps[i].subs
        var j = subs.indexOf(this)
        if (j > -1) subs.splice(j, 1)
    }
}

module.exports = Binding