Question

我有以下哈希数组。我正在尝试遍历它，并构建一个ID和product_order_id值的哈希数组。

 select * 
   from (
         select *
                ,row_number() over(partition by date_trunc('day',a.readtime) order by a.readtime asc ) as rnk
           from university.gas_ert a
         )x
   where x.rnk=1

这应该是它的样子

let db;
let request = window.indexedDB.open("Cities", 1);

request.onerror = function (event) {
    console.log("error")
};
request.onsuccess = function (event) {

    db = event.target.result;
    document.getElementById('search').addEventListener('click',function () {

        let transaction = db.transaction(["City"], "readwrite");

        transaction.oncomplete = function () {
            document.querySelector('body').innerHTML += '<li>Transaction completed.</li>';
        };

        transaction.onerror = function (event) {
            document.querySelector('body').innerHTML += '<li>Transaction not opened due to error: ' + transaction.error + '</li>';
        };

        let objectStore = transaction.objectStore("City");

        let objectStoreRequest = objectStore.getAll();

        objectStoreRequest.onsuccess = function () {
            document.querySelector('body').innerHTML += '<li>Request successful.</li>';
            let myRecord;
            myRecord = objectStoreRequest.result;
            console.log(myRecord)
        }
    })
};

我尝试这样做，但是没有运气

objects = 
[
  #<Product: 0x00007ffd4a561108
  @id="1",
  @product_id="2",
  @product_order_id="23",
  @description="abc",
  @status="abcde",
  @start_date=nil,
  @end_date=nil>,
  #<Product: 0x00007ffd4a560c80
  @id="45",
  @product_id="22",
  @product_order_id="87",
  @description="ahef",
  @status="gesff",
  @start_date=nil,
  @end_date=nil>
......more objects.....
    ]

有什么主意吗？

Answer 1

内联解决方案：

> Hash[objects.map{|p| [p.id, p.product_order_id] }]
# Output : [{ 1=>23 }, { 45=>87 }]

Answer 2

我通常会使用each_with_object

来实现它

objects.each_with_object({}) { |obj, acc| acc[obj.id] = obj.product_order_id }

除非我真的想降低性能，否则我会选择Gagan's answer

Answer 3

您尝试过吗？

def mapped_product(objects)
    mapping = []
    objects.each do |object|
      mapping << {
        object.id => object.product_order_id # I'm using an `=>` here
      }
    end
    mapping # return the new mapping
end

我刚刚将:的哈希值上的=>更改为“使其动态”，并交换了id和product_order_id的值

您也可以在此处使用map

def mapped_product(objects)
    objects.map do |object|
     {  object.id => object.product_order_id }
    end
end

如何通过遍历对象数组来创建哈希数组

3 个答案: