Delphi从JSON对象访问数据 [英] Delphi accessing data from json object

问题描述

我需要编写一些代码来从我的应用程序将从网站接收的JSON字符串中检索数据。

I need to write some code to retrieve data from a JSON string that my application will receive from a web site.

这是JSON字符串。

This is the JSON string.

{
  "client" :
     {
      "Name" : "john doe",
      "Phone" : 12345678,
      "Address": "5th av",
     },
  "order" : [
     {
      "Code" : 101,
      "Quantity" : 1,
      "Cost": 10.50,
      "Coment" : ""
     },
     {
      "Code" : 102,
      "Quantity" : 3,
      "Cost": 8.50,
      "Coment" : ""
     },
     {
      "Code" : 103,
      "Quantity" : 1,
      "Cost": 21.50,
      "Coment" : ""
     }
  ]
}

我对如何读取对和数组感到非常困惑。我已经尝试过在此处和其他论坛上发布的许多代码，但仍然无法完成。

I am getting very confused about how to read pairs and arrays. I've tried lots of code posted here and other forums, but I still cannot get it done.

有人可以给我一些提示来完成它吗？我正在使用XE5和JSON单元。

Can anyone give me some hints to get it done? I am using XE5 and JSON units.

推荐答案

我不会为您编写实际的代码，但是我要提示。

I'm not going to write the actual code for you, but I am going to give you a hint.

这是显示的JSON结构：

Here is the structure of the JSON you have shown:

object
|
|_ client (object)
|  |_ Name (string)
|  |_ Phone (string)
|  |_ Address (string)
|
|_ order (array)
  |_ [0] (object)
  |  |_ Code (number)
  |  |_ Quantity (number)
  |  |_ Code (number)
  |  |_ Coment (string)
  |
  |_ [1] (object)
  |  |_ Code (number)
  |  |_ Quantity (number)
  |  |_ Code (number)
  |  |_ Coment (string)
  |
  |_ [2] (object)
     |_ Code (number)
     |_ Quantity (number)
     |_ Code (number)
     |_ Coment (string)

您可以将<一对一映射到 Data.DBXJSON 单元（它们已移至 System.JSON 单元）。

You can map that 1-to-1 to Delphi's native JSON classes in the Data.DBXJSON unit (they were moved to the System.JSON unit in XE6).

1. 首先将JSON字符串传递给 TJSONObject.ParseJSONValue（） ，它返回 TJSONValue 。将该类型键入到 TJSONObject 。


2. 使用其 值 属性可访问客户端和订单值。将它们键入到 TJSONObject 和分别是 TJSONArray 。


3. 对于客户端对象，请使用其 Values 属性访问 Name ， Phone 和 Address 值。您可以调用其 Value（） 方法获取其字符串值。


4. 对于 order 数组，使用其 Count 和 Items 属性，或其 GetEnumerator 方法（间接在 for..in 循环，以遍历数组项，然后将每个项键入到 TJSONObject 中进行访问其 Values 属性。数字值，将它们键入到 TJSONNumber 访问其 AsInt ， AsInt64 和 AsDouble 属性。

1. Start by passing the JSON string to TJSONObject.ParseJSONValue(), which returns a TJSONValue. Type-cast that to a TJSONObject.
2. Use its Values property to access the client and order values. Type-cast them to TJSONObject and TJSONArray, respectively.
3. For the client object, use its Values property to access the Name, Phone, and Address values. You can call their Value() method to get their string values.
4. for the order array, use its Count and Items properties, or its GetEnumerator method (indirectly in a for..in loop, to iterate through the array items. Type-cast each one to a TJSONObject to access its Values property. For the number values, type-cast them to TJSONNumber to access their AsInt, AsInt64, and AsDouble properties as needed.

有关更多信息，请参见Embarcadero的 JSON文档。

See Embarcadero's JSON documentation for more information.

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