Delphi解析JSON数组或数组 [英] Delphi parse JSON array or array
问题描述
这是我希望能够解析的示例JSON:
This is the sample JSON I want to be able to parse:
[
{
"a":{
"username":"aaa",
"email":"aaa@gmail.com"
}
},
{
"b":{
"username":"bbb",
"email":"bbb@gmail.com"
}
}
]
我需要对getData('b', 'email')的调用必须输出bbb@gmail.com！
I need that a call to getData('b', 'email') must output bbb@gmail.com!
我真的很努力地了解如何使用System.JSON单元，但是我找不到解决方案！我希望能够编写一个从上述JSON结构中提取特定数据的函数.到目前为止，这是我的代码.在类构造函数中，我有:
I am really struggling to understand how to use the System.JSON unit, but I can't get the solution! I want to be able to write a function that extracts a particular data from the above kind of JSON structure. This is my code so far. In the class constructor I have:
var
FIds: TJSONArray;
begin
FIds := TJSONObject.ParseJSONValue({json string here}) as TJSONArray;
end;
然后，在必须返回数据的函数中，我这样写:
Then, inside the function that must return the data, I have written this:
// 'name' can be 'a' or 'b' | 'data' can be 'username' or 'email'
function TTest.getData(const name, data: string): string;
var
FValue, FValueInner: TJSONValue;
begin
for FValue in Fids do
begin
if (FValue is TJSONArray) then
begin
//Here I am sure that I have a TJSONArray (which can be 'a' or 'b' from above)
end;
end;
end;
根据上面的内容，我必须检查name的值并确定是否必须访问a或b中的数据.然后，一旦选择了正确的JSON数组a或b，就必须选择是否要显示username或email字段(在data变量中指定).
According to what I have written above, I have to check the value of name and decide if I have to access the data inside a or b. Then, once I have picked the correct JSON array a or b, I have to select if I want to display the username or the email field (which is specified inside the data variable).
我该怎么做?
这是我最近的尝试，但我真的不知道该怎么办:
This is my latest attempt but I really can't understand what to do:
... same code above ...
if (FValue is TJSONArray) then
begin
//here I want to check if the current array is a or b
if ((FValue as TJSONArray).Items[0] as TJSONValue).Value = name then
begin
Farr := TJSONObject.ParseJSONValue(((FValue as TJSONArray).Items[0] as TJSONValue).ToJSON) as TJSONArray;
try
//here I want to get the data inside username or email
for FValueInner in Farr do
Result := FValueInner.GetValue<string>(data);
finally
Farr.Free;
end;
end;
end;
Farr: TJSONArray;和FValueInner: TJSONValue;
推荐答案
面向寻求这些答案的新读者.
For new readers looking for these answers.
该功能如何?如果重新构建JSON数据，甚至更简单?
How about this function, or even simpler if you restructure the JSON data?
function getData(JsonString: String; User: String; Field: String): String;
var
JSonValue: TJSonValue;
JsonArray: TJSONArray;
ArrayElement: TJSonValue;
FoundValue: TJSonValue;
begin
Result :='';
// create TJSonObject from string
JsonValue := TJSonObject.ParseJSONValue(JsonString);
// get the array
JsonArray := JsonValue as TJSONArray;
// iterate the array
for ArrayElement in JsonArray do begin
FoundValue := ArrayElement.FindValue(User);
if FoundValue <> nil then begin
Result := ArrayElement.GetValue<string>(User + '.' + Field);
break;
end;
end;
end;
上面的示例JSON代码的问题在于，它使用用户名"a""b"作为用户数据的 JSON键 {key:data}.这样，您就无法在数据搜索中使用GetValue("a").以不同的方式构造JSON数据使搜索过程更加容易.稍后，我将举一个例子.
The problem with the sample JSON code above is that it uses the users' names "a" "b" as a JSON-key {key:data} for the users' data. In this way you can't use GetValue("a") in your search for data. Structuring your JSON data differently makes the search process a lot easier. I will later on give an example of this.
处理给定JSON数据的一种方法是使用 FindValue ，因此您可以检查是否具有 key 的字段strong>存在"a"或"b".
A way to handle the given JSON data is by using FindValue so you can check if a field with key "a" or "b" exists.
FoundValue := ArrayElement.FindValue("b");
if FoundValue <> nil then begin
Result := ArrayElement.GetValue<string>("b"+ '.' + "email");
break;
关于"解析JSON数组"问题:将数据作为TJSonObject加载后，您可以将数据更改为TJSONArray并迭代元素.
About the 'parsing a JSON array' question: After the data is loaded as a TJSonObject you can change the data into a TJSONArray and iterate the elements.
JsonValue := TJSonObject.ParseJSONValue(JsonString);
JsonArray := JsonValue as TJSONArray;
for ArrayElement in JsonArray do begin
...
给定JSON数据的有效示例代码:
unit JsonArray1;
interface
uses System.JSON;
function getData2(JsonString: String; User: String; Field: String): String;
procedure Test1();
implementation
function getData2(JsonString: String; User: String; Field: String): String;
var
JSonValue: TJSonValue;
JsonArray: TJSONArray;
ArrayElement: TJSonValue;
FoundValue: TJSonValue;
begin
Result :='';
// create TJSonObject from string
JsonValue := TJSonObject.ParseJSONValue(JsonString);
// get the array
JsonArray := JsonValue as TJSONArray;
// iterate the array
for ArrayElement in JsonArray do begin
FoundValue := ArrayElement.FindValue(User);
if FoundValue <> nil then begin
Result := ArrayElement.GetValue<string>(User + '.' + Field);
break;
end;
end;
end;
procedure Test1();
var
DataBase: String;
EmailAddress : String;
Username: String;
begin
DataBase := '[ {"a" : {"username":"aaa","email":"aaa@gmail.com"}},' +
'{"b" : {"username":"bbb","email":"bbb@gmail.com"}} ]';
EmailAddress := getData2(DataBase, 'b', 'email');
Username := getData2(DataBase, 'a', 'username');
end;
end.
如前所述，使用适当的键重组JSON数据可使代码查找数据更加简单.由于用户数据"a":{}，"b":{}之间存在一对一的关系，因此很容易引入用户"密钥.另外，在数组中添加用户"键也会导致所有数据都具有键.
As already mentioned, restructuring the JSON data with proper keys makes the code to find data more simple. Because there is a 1 on 1 relation between the users' data "a":{}, "b":{} it's easy to introduce a 'user' key. Also adding a 'users' key to the array results in all data having keys.
'{"users" : [{ "user":"a", "username":"aaa","email":"aaa@gmail.com"},' +
'{ "user":"b", "username":"bbb","email":"bbb@gmail.com"}]}';
迭代用户时，现在可以将GetValue与新的用户"键一起使用.
When you iterate the users, you can now use GetValue with the new "user" key.
if ArrayElement.GetValue<String>('user') = 'b' then begin
Result := ArrayElement.GetValue<String>('email');
通过为数组提供键，您现在可以使用以下命令获取数组:
By giving the array a key you can now get the array with:
JsonArray := JsonValue.GetValue<TJSONArray>('users');
重构后的JSON数据的工作示例代码:
unit JsonArray2;
interface
uses System.JSON;
function getData2(JsonString: String; User: String; Field: String): String;
procedure Test2();
implementation
function getData2(JsonString: String; User: String; Field: String): String;
var
JSonValue: TJSonValue;
JsonArray: TJSONArray;
ArrayElement: TJSonValue;
FoundValue: TJSonValue;
begin
Result :='';
// create TJSonObject from string
JsonValue := TJSonObject.ParseJSONValue(JsonString);
// get the array
JsonArray := JsonValue.GetValue<TJSONArray>('users');
// iterate the array
for ArrayElement in JsonArray do begin
if ArrayElement.GetValue<String>('user') = User then begin
Result := ArrayElement.GetValue<String>(Field);
break;
end;
end;
end;
procedure Test2();
var
DataBase: String;
EmailAddress : String;
Username: String;
begin
DataBase := '{"users" : [{ "user":"a", "username":"aaa","email":"aaa@gmail.com"},' +
'{ "user":"b", "username":"bbb","email":"bbb@gmail.com"}]}';
EmailAddress := getData2(DataBase, 'b', 'email');
Username := getData2(DataBase, 'a', 'username');
end;
end.
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