用户可以自由更新或删除其 Google 日历活动。如果用户在为会议创建事件后更新了该事件，您的插件可能需要通过更新会议数据来响应更改。如果您的第三方会议系统依赖于跟踪活动数据，那么在活动发生变化时未更新会议可能会导致会议无法使用，并造成糟糕的用户体验。
随着 Google 日历活动的更改而更新会议数据的过程称为同步。您可以创建一个 Apps 脚本可安装触发器来同步活动更改，该触发器会在给定日历中的事件发生更改时触发。遗憾的是，该触发器不会报告哪些事件发生了更改，因此您无法将其限制为仅包含您创建的会议的事件。而是必须请求获取自上次同步以来对日历所做的所有更改的列表，过滤事件列表，然后相应地进行更新。
一般同步流程如下：
- 用户首次创建会议时，系统会初始化同步流程。
- 每当用户创建、更新或删除其日历活动时，触发器都会在您的插件项目中执行触发器函数。
- 触发器函数会检查上次同步后发生的一组事件更改，并确定是否需要更新关联的第三方会议。
- 所有必要的更新均通过发出第三方 API 请求对会议进行。
- 系统会存储新的同步令牌，以便下次触发器执行时只需检查日历的最新更改。
初始化同步
插件在第三方系统上成功创建会议后，应该创建一个可安装的触发器，用于响应此日历中的事件更改（如果触发器尚不存在）。
创建触发器后，初始化应通过创建初始同步令牌完成。为此，您可以直接执行触发器函数。
创建日历触发器
如要进行同步，您的插件需要检测包含会议的日历活动何时更改。此操作通过创建 EventUpdated
可安装触发器来实现。您的插件只需为每个日历创建一个触发器，并且可以通过编程方式创建这些触发器。
创建触发器的最佳时机是用户创建第一场会议时，因为那时用户就会开始使用该插件。创建会议并验证没有错误后，您的插件应检查此用户是否存在触发器，如果没有，则创建触发器。
实现同步触发器函数
当 Apps Script 检测到导致触发器触发的条件时，就会执行触发器函数。当用户在指定日历中创建、修改或删除任何活动时，EventUpdated 日历触发器会触发。
您必须实现您的插件使用的触发器函数。此触发器函数应执行以下操作：
- 使用
syncToken调用日历高级服务Calendar.Events.list()，以检索自上次同步后发生更改的活动列表。通过使用同步令牌，您可以减少您的插件必须检查的事件数量。如果触发器函数在执行时没有有效的同步令牌，则会回退到完整同步。完整同步只是尝试检索规定时间范围内的所有事件，以生成新的有效同步令牌。
- 系统会检查每个经过修改的事件，以确定其是否有关联的第三方会议。
- 如果活动有会议，系统会对其进行检查，了解发生了哪些变化。根据具体更改，您可能需要修改关联的会议。例如，如果删除了某个活动，该插件可能也会一并删除会议。
- 如需对会议进行任何必要的更改，只需向第三方系统发出 API 调用即可。
- 进行所有必要的更改后，存储
Calendar.Events.list()方法返回的nextSyncToken。此同步令牌位于Calendar.Events.list()调用返回的最后一页结果中。
更新 Google 日历活动
在某些情况下，您可能需要在执行同步时更新 Google 日历活动。如果您选择执行此操作，请通过相应的 Google 日历高级服务请求更新活动。请务必将条件更新与 If-Match 标头搭配使用。这可以防止您的更改意外覆盖用户在其他客户端中进行的并发更改。
示例
以下示例展示了如何为日历活动及其关联的会议设置同步。
/**
* Initializes syncing of conference data by creating a sync trigger and
* sync token if either does not exist yet.
*
* @param {String} calendarId The ID of the Google Calendar.
*/
function initializeSyncing(calendarId) {
// Create a syncing trigger if it doesn't exist yet.
createSyncTrigger(calendarId);
// Perform an event sync to create the initial sync token.
syncEvents({'calendarId': calendarId});
}
/**
* Creates a sync trigger if it does not exist yet.
*
* @param {String} calendarId The ID of the Google Calendar.
*/
function createSyncTrigger(calendarId) {
// Check to see if the trigger already exists; if does, return.
var allTriggers = ScriptApp.getProjectTriggers();
for (var i = 0; i < allTriggers.length; i++) {
var trigger = allTriggers[i];
if (trigger.getTriggerSourceId() == calendarId) {
return;
}
}
// Trigger does not exist, so create it. The trigger calls the
// 'syncEvents()' trigger function when it fires.
var trigger = ScriptApp.newTrigger('syncEvents')
.forUserCalendar(calendarId)
.onEventUpdated()
.create();
}
/**
* Sync events for the given calendar; this is the syncing trigger
* function. If a sync token already exists, this retrieves all events
* that have been modified since the last sync, then checks each to see
* if an associated conference needs to be updated and makes any required
* changes. If the sync token does not exist or is invalid, this
* retrieves future events modified in the last 24 hours instead. In
* either case, a new sync token is created and stored.
*
* @param {Object} e If called by a event updated trigger, this object
* contains the Google Calendar ID, authorization mode, and
* calling trigger ID. Only the calendar ID is actually used here,
* however.
*/
function syncEvents(e) {
var calendarId = e.calendarId;
var properties = PropertiesService.getUserProperties();
var syncToken = properties.getProperty('syncToken');
var options;
if (syncToken) {
// There's an existing sync token, so configure the following event
// retrieval request to only get events that have been modified
// since the last sync.
options = {
syncToken: syncToken
};
} else {
// No sync token, so configure to do a 'full' sync instead. In this
// example only recently updated events are retrieved in a full sync.
// A larger time window can be examined during a full sync, but this
// slows down the script execution. Consider the trade-offs while
// designing your add-on.
var now = new Date();
var yesterday = new Date();
yesterday.setDate(now.getDate() - 1);
options = {
timeMin: now.toISOString(), // Events that start after now...
updatedMin: yesterday.toISOString(), // ...and were modified recently
maxResults: 50, // Max. number of results per page of responses
orderBy: 'updated'
}
}
// Examine the list of updated events since last sync (or all events
// modified after yesterday if the sync token is missing or invalid), and
// update any associated conferences as required.
var events;
var pageToken;
do {
try {
options.pageToken = pageToken;
events = Calendar.Events.list(calendarId, options);
} catch (err) {
// Check to see if the sync token was invalidated by the server;
// if so, perform a full sync instead.
if (err.message ===
"Sync token is no longer valid, a full sync is required.") {
properties.deleteProperty('syncToken');
syncEvents(e);
return;
} else {
throw new Error(err.message);
}
}
// Read through the list of returned events looking for conferences
// to update.
if (events.items && events.items.length > 0) {
for (var i = 0; i < events.items.length; i++) {
var calEvent = events.items[i];
// Check to see if there is a record of this event has a
// conference that needs updating.
if (eventHasConference(calEvent)) {
updateConference(calEvent, calEvent.conferenceData.conferenceId);
}
}
}
pageToken = events.nextPageToken;
} while (pageToken);
// Record the new sync token.
if (events.nextSyncToken) {
properties.setProperty('syncToken', events.nextSyncToken);
}
}
/**
* Returns true if the specified event has an associated conference
* of the type managed by this add-on; retuns false otherwise.
*
* @param {Object} calEvent The Google Calendar event object, as defined by
* the Calendar API.
* @return {boolean}
*/
function eventHasConference(calEvent) {
var name = calEvent.conferenceData.conferenceSolution.name || null;
// This version checks if the conference data solution name matches the
// one of the solution names used by the add-on. Alternatively you could
// check the solution's entry point URIs or other solution-specific
// information.
if (name) {
if (name === "My Web Conference" ||
name === "My Recorded Web Conference") {
return true;
}
}
return false;
}
/**
* Update a conference based on new Google Calendar event information.
* The exact implementation of this function is highly dependant on the
* details of the third-party conferencing system, so only a rough outline
* is shown here.
*
* @param {Object} calEvent The Google Calendar event object, as defined by
* the Calendar API.
* @param {String} conferenceId The ID used to identify the conference on
* the third-party conferencing system.
*/
function updateConference(calEvent, conferenceId) {
// Check edge case: the event was cancelled
if (calEvent.status === 'cancelled' || eventHasConference(calEvent)) {
// Use the third-party API to delete the conference too.
} else {
// Extract any necessary information from the event object, then
// make the appropriate third-party API requests to update the
// conference with that information.
}
}