getTeam method
读取群组
Implementation
Team getTeam(ObjectId tid) {
var item = _teamMap[tid];
if (item == null) {
//创建一个临时群组实例
item = Team(bsid: DbQueryField.hexstr2ObjectId(bsid), id: tid);
_teamMap[tid] = item;
//获取未缓存的群组信息
teamFetch(tids: [tid]);
}
return item;
}