执行回调一次每个异步任务完成forEach

Question

我正在编写一些PostgreSQL事务，并且我需要执行一次回调，forEach中的每个函数都已执行。下面是一些代码：

var sql = "BEGIN;UPDATE object SET name = "+data.name+", object_subtype_id = "+data.object_subtype_id+" WHERE id = "+data.id+";"; 
db.driver.execQuery(sql, function(err, result) { 
    data.object_subtype.object_property_type.forEach(function(item) { 
    db.driver.execQuery("WITH upsert AS (UPDATE object_property SET value = '"+item.value+"' WHERE object_property_type_id = "+item.id+" AND object_id = "+data.id+" RETURNING *) INSERT INTO object_property (object_property_type_id, object_id, value) SELECT "+item.id+", "+data.id+", '"+item.value+"' WHERE NOT EXISTS (SELECT * FROM upsert);", function(err, nb) { 
     // I need to send the COMMIT; here once all the functions in the forEach have been executed 
    }); 
    }); 
}); 

我在async了一下，但我不知道怎么样，还是我，它适用于我的情况。

有什么想法吗？

谢谢！

Answer 1

结合async.series和async.each你会与这个美丽的片段结束：

var sql = "BEGIN;UPDATE object SET name = "+data.name+", object_subtype_id = "+data.object_subtype_id+" WHERE id = "+data.id+";"; 

async.series([ 
    function (next) { 
    db.driver.execQuery(sql, next); 
    }, 
    function (next) { 
    async.each(data.object_subtype.object_property_type, function (item, next) { 
     db.driver.execQuery("WITH upsert AS (UPDATE object_property SET value = '"+item.value+"' WHERE object_property_type_id = "+item.id+" AND object_id = "+data.id+" RETURNING *) INSERT INTO object_property (object_property_type_id, object_id, value) SELECT "+item.id+", "+data.id+", '"+item.value+"' WHERE NOT EXISTS (SELECT * FROM upsert);", next); 
    }, next); 
    } 
], function (err, results) { 
    // Not sure what you want to do with the result 
}); 

它可能需要一些调整，这取决于你希望与什么样的结果。

Answer 2

如果你不想使用异步（它有时使简单的应用程序复杂）JS的做法是通过引用计数。做这个;

var sql = "BEGIN;UPDATE object SET name = "+data.name+", object_subtype_id = "+data.object_subtype_id+" WHERE id = "+data.id+";"; 
db.driver.execQuery(sql, function(err, result) { 
    var counter =0; 
    data.object_subtype.object_property_type.forEach(function(item) { 
    db.driver.execQuery("WITH upsert AS (UPDATE object_property SET value = '"+item.value+"' WHERE object_property_type_id = "+item.id+" AND object_id = "+data.id+" RETURNING *) INSERT INTO object_property (object_property_type_id, object_id, value) SELECT "+item.id+", "+data.id+", '"+item.value+"' WHERE NOT EXISTS (SELECT * FROM upsert);", function(err, nb) { 
     //THIS IS WHERE REFERENCE COUNTING HAPPENS 
     counter++; 
     if(counter === data.subtype.type.length) { 
      COMMIT (since all callback functions returned 
     } 
     // I need to send the COMMIT; here once all the functions in the forEach have been executed 
    }); 
    }); 
});