[英]Parse cloud function - code ot executed in sequence
我有下面的函数来更新行,如果满足某些条件,并且在for循环结束时,响应包括更新了多少行。尽管更新的行多于零,但响应显示为零。 查看日志,似乎在完成for循环之前会触发reponse.success()。
为什么这样?
Parse.Cloud.define("reset", function(request, response) {
var isSaveNeeded = false
var Query = new Parse.Query("price");
Query.equalTo('isActive', true);
Query.find({useMasterKey:true})
.then((results) => {
console.log("Found " + results.length + " price rows")
var currentDate = moment()
var noOfRowsUpdated = 0
for (let i = 0; i < results.length; ++i) {
var valid_till_date = results[i].get('valid_till_date');
if (valid_till_date == null) {
// if user had not selected valid_till_date then set to expire after system max no of days
var updatedAt = results[i].get('updatedAt');
if (currentDate.diff(updatedAt,'days') > 10) {
console.log("Permanent change row to be set inactive. Updated at - " + currentDate.diff(updatedAt)+ updatedAt)
results[i].set('isActive',false)
isSaveNeeded = true
}
} else if (currentDate.diff(valid_till_date) > 0) {
// check whether valid_till_date has passed
console.log("Found row with elapsed valid date " + results[i].id)
results[i].set("isActive",false)
isSaveNeeded = true
}
if (isSaveNeeded == true) {
console.log("Record needs to be saved for " + results[i].id)
results[i].save(null, {useMasterKey:true})
.then(function (user) {
++noOfRowsUpdated
console.log("reset : Object ID: " + results[i].id + " saved - " + noOfRowsUpdated)
})
.catch(function (error) {
console.log("reset : Error saving Object ID: " + results[i].id + error);
response.error(error);
})
} else {
console.log("Record not to be saved for " + results[i].id)
}
isSaveNeeded = false
} // end of for loop
//BELOW IS EXECUTED BEFORE FOR LOOP COMPLETES
console.log("Updated " + noOfRowsUpdated +" price rows");
response.success("Updated " + noOfRowsUpdated +" price rows")
}) // end of .then((results)
.catch(function(error) {
response.error("Failed to fetch from price" + error );
});
});
Parse.com的save
异步运行,因此循环在保存发生之前完成。 解决方案是稍微重组代码,并在执行响应功能之前等待保存完成。
诀窍是将每个保存的返回的诺言收集到一个数组中,并等待Promise.when()
( Promise.when()
同义词Promise.when()
实现这些诺言
为了更加清楚,请排除“需要保存”逻辑,因此该云功能只能用于处理数据库。
Parse.Cloud.define("reset", function(request, response) {
var Query = new Parse.Query("price");
Query.equalTo('isActive', true);
Query.find({useMasterKey:true}).then((results) => {
console.log("Found " + results.length + " price rows");
// assuming ES6 or something like underscore
let pricesToSave = results.filter(price => priceNeedsSave(price));
// here's the important part, collect the promise from each save
// proceed only after the promises have completed
let promises = pricesToSave.map(price => price.save(null, {useMasterKey:true}));
return Parse.Promise.when(promises).then(() => pricesToSave.length);
}).then(count => {
response.success("Updated " + count +" price rows");
}).catch(error => {
response.error("Failed to fetch from price" + error );
});
}
为了完整起见,下面是分解式的requireSave逻辑。 (OP应该检查一下,我只是复制了循环的主体)...
function priceNeedsSave(price) {
var isSaveNeeded = false;
var currentDate = moment()
var valid_till_date = price.get('valid_till_date');
if (valid_till_date == null) {
// if user had not selected valid_till_date then set to expire after system max no of days
var updatedAt = price.get('updatedAt');
if (currentDate.diff(updatedAt,'days') > 10) {
console.log("Permanent change row to be set inactive. Updated at - " + currentDate.diff(updatedAt)+ updatedAt)
price.set('isActive',false)
isSaveNeeded = true
}
} else if (currentDate.diff(valid_till_date) > 0) {
// check whether valid_till_date has passed
console.log("Found row with elapsed valid date " + price.id)
price.set("isActive",false)
isSaveNeeded = true
}
return isSaveNeeded;
}
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