用户可以自由更新或删除其 Google 日历活动。如果用户在为活动创建会议后对其进行更新，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事件数据，则未能根据活动更改更新视频会议会导致会议无法使用，并导致糟糕的用户体验。
将会议数据随 Google 日历活动的更改保持更新的过程称为“同步”。您可以通过创建 Apps 脚本可安装触发器来同步事件更改，该触发器会在指定日历中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变化，您也无法将该功能限制为仅包含您创建的会议中的事件。您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，并相应地进行更新。
常规同步过程如下：
- 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、更新或删除某个日历活动时，触发器都会在您的插件项目中执行一个触发函数。
- 触发器函数会检查自上次同步以来的一组事件更改，并确定是否需要更新关联的第三方会议。
- 通过发出第三方 API 请求对视频会议进行所有必要的更新。
- 系统会存储新的同步令牌，以便下一次触发器执行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，应创建一个可安装的触发器来响应此日历中事件更改（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来完成。具体方法是直接执行触发器函数。
创建日历触发器
为了进行同步，您的插件需要检测包含附加会议的日历活动何时发生了更改。这通过创建 EventUpdated
可安装触发器来实现。插件每个日历只需要一个触发器，并且可通过编程方式创建。
创建触发器的最佳时机是在用户创建其第一个会议时，因为此时用户就开始使用该插件。创建会议并确认没有错误后，您的插件应检查该用户是否存在触发器，如果不存在，则会触发该触发器。
实现同步触发器函数
当 Apps 脚本检测到导致触发器触发的条件时，系统会执行触发函数。EventUpdated 日历触发器会在用户创建、修改或删除指定日历中的任意活动时触发。
您必须实现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进行日历高级服务Calendar.Events.list()调用，以检索自上次同步后更改的事件列表。通过使用同步令牌，您可以减少插件必须检查的事件数量。如果触发器函数在没有有效的同步令牌的情况下执行，则会退避到完全同步。完全同步只是尝试检索规定时间范围内的所有事件，以生成新的有效的同步令牌。
- 系统会检查每个修改后的事件，以确定其是否具有关联的第三方会议。
- 如果活动有一场会议，系统会对其进行检查，以了解发生了哪些变化。 您可能需要修改关联的会议，具体取决于相应的变更。例如，如果删除了活动，则插件可能也应删除会议。
- 通过对第三方系统进行 API 调用，对会议进行所需的任何更改。
- 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()调用返回的结果的最后一页。
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，请使用相应的 Google 日历高级服务请求更新活动。请务必对 If-Match 标头使用条件更新。这样可以防止您的更改无意中覆盖用户在其他客户端中所做的并发更改。
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.
}
}