如何使用云代码在Parse中保存多对多关系？

Question

基本上，在我的users表中，我有一个列canHave，它是一个对象列表Event。所以我的Users和Event表

之间存在多对多的关系

这是我的代码（云代码）：

  Parse.Cloud.define("updateUserCanHave", function (request, response) {
    var query = new Parse.Query(Parse.User);
    query.equalTo("email", request.params.mail);
    query.find({
        success: function (myUser) {

            var newUser = myUser[0];
            var myRelation = newUser.relation("canHave");

            var eventsQuery = newUser.relation('canHave').query();
            eventsQuery.find().then(function (events) {
                myRelation.remove(events[0]);
            });

            newUser.save(null, {useMasterKey: true})
            response.success();
        }
    }).catch(function (error) {
        response.error("Error " + error.code + " : " + error.message + " when updating user canHave.");
    });
});

但是我的用户永远不会改变，我的功能参数也很好。

Answer 1

newUser.save()将开始异步执行，然后通过同步调用response.success()立即终止。通过保存后将响应放在执行顺序中进行修复。

我更喜欢这些调用的promise-returns表单，但如果你的样式是回调函数......

newUser.save(null, {
    useMasterKey: true,
    success: function(result) {
        // moved here, after the save succeeds
        response.success(result);
    },
    error: function(result, error) {
        response.error(error);
    }
});

编辑代码在关系查询中存在相同问题。使用回调样式方法很难清楚（甚至看到问题）。使用承诺......

function findUserByEmail(email) {
    let query = new Parse.Query(Parse.User);
    query.equalTo("email", email);
    return query.first();  // notice "first" here, if we're going to use only the first anyway
}

Parse.Cloud.define("updateUserCanHave", function (request, response) {
    var user;
    findUserByEmail(request.params.mail).then(_user => {
        user = _user;
        return user.relation("canHave").query().first();
        // I left your relation query in here.  In general, you don't
        // have to query before removing it, but maybe your app logic requires this
        // in other words, you could just do the remove and save here, and skip the next then block
    }).then(event => {
        if (event) user.relation("canHave").remove(event);
        return user.save(null, { useMasterKey: true });
    }).then(() => {
        response.success();
    }).catch(error => {
        response.error(error);
    });
});