avalon2/src/vmodel/transaction.js

an elegant efficient express mvvm framework

import { avalon, config } from '../seed/core'

avalon.pendingActions = []
avalon.uniqActions = {}
avalon.inTransaction = 0
config.trackDeps = false
avalon.track = function() {
    if (config.trackDeps) {
        avalon.log.apply(avalon, arguments)
    }
}

/**
 * Batch is a pseudotransaction, just for purposes of memoizing ComputedValues when nothing else does.
 * During a batch `onBecomeUnobserved` will be called at most once per observable.
 * Avoids unnecessary recalculations.
 */


export function runActions() {
    if (avalon.isRunningActions === true || avalon.inTransaction > 0)
        return
    avalon.isRunningActions = true
    var tasks = avalon.pendingActions.splice(0, avalon.pendingActions.length)
    for (var i = 0, task; task = tasks[i++];) {
        task.update()
        delete avalon.uniqActions[task.uuid]
    }
    avalon.isRunningActions = false
}


export function propagateChanged(target) {
    var list = target.observers
    for (var i = 0, el; el = list[i++];) {
        el.schedule(); //通知action, computed做它们该做的事
    }
}

//将自己抛到市场上卖
export function reportObserved(target) {
    var action = avalon.trackingAction || null
    if (action !== null) {

        avalon.track('征收到', target.expr)
        action.mapIDs[target.uuid] = target;
    }

}


var targetStack = []

export function collectDeps(action, getter) {
    if (!action.observers)
        return
    var preAction = avalon.trackingAction
    if (preAction) {
        targetStack.push(preAction)
    }
    avalon.trackingAction = action
    avalon.track('【action】', action.type, action.expr, '开始征收依赖项')
        //多个observe持有同一个action
    action.mapIDs = {} //重新收集依赖
    var hasError = true,
        result
    try {
        result = getter.call(action)
        hasError = false
    } finally {
        if (hasError) {
            avalon.warn('collectDeps fail', getter + '')
            action.mapIDs = {}
            avalon.trackingAction = preAction
        } else {
            // 确保它总是为null
            avalon.trackingAction = targetStack.pop()
            try {
                resetDeps(action)
            } catch (e) {
                avalon.warn(e)
            }
        }
        return result
    }

}


function resetDeps(action) {
    var prev = action.observers,
        curr = [],
        checked = {},
        ids = []
    for (let i in action.mapIDs) {
        let dep = action.mapIDs[i]
        if (!dep.isAction) {
            if (!dep.observers) { //如果它已经被销毁
                delete action.mapIDs[i]
                continue
            }
            ids.push(dep.uuid)
            curr.push(dep)
            checked[dep.uuid] = 1
            if (dep.lastAccessedBy === action.uuid) {
                continue
            }
            dep.lastAccessedBy = action.uuid
            avalon.Array.ensure(dep.observers, action)
        }
    }
    var ids = ids.sort().join(',')
    if (ids === action.ids) {
        return
    }
    action.ids = ids
    if (!action.isComputed) {
        action.observers = curr
    } else {
        action.depsCount = curr.length
        action.deps = avalon.mix({}, action.mapIDs)
        action.depsVersion = {};
        for (let i in action.mapIDs) {
            let dep = action.mapIDs[i]
            action.depsVersion[dep.uuid] = dep.version
        }
    }

    for (let i = 0, dep; dep = prev[i++];) {
        if (!checked[dep.uuid]) {
            avalon.Array.remove(dep.observers, action)
        }
    }

}



function transaction(action, thisArg, args) {
    args = args || []
    var name = 'transaction ' + (action.name || action.displayName || 'noop')
    transactionStart(name)
    var res = action.apply(thisArg, args)
    transactionEnd(name)
    return res
}
avalon.transaction = transaction

export function transactionStart(name) {
    avalon.inTransaction += 1;
}

export function transactionEnd(name) {
    if (--avalon.inTransaction === 0) {
        avalon.isRunningActions = false
        runActions()
    }
}