创建树状结构的 JSON

Question

我有一个 TDepartment 类型的对象列表，看起来像这样

TDepartment = class
  ID : Integer;
  Name : string;
  ParentDepartmentID : Integer;
end;

我需要创建一个 TJSONObject，其中包含一个部门数组，它们都可以有一个部门数组。所以它的深度是未知的。

我现在处于一个对我来说根本没有意义的地步，但我希望生成的 JSON 看起来像这样：

    "department_id": "5",
    "department_name": "100",
    "parent_dept_id": "",
    "subdepartments": [{
        "department_id": "8",
        "department_name": "300",
        "parent_dept_id": "5",
        "subdepartments": [{
            "department_id": "1",
            "department_name": "310",
            "parent_dept_id": "8",
            "subdepartments": []

请记住，每个级别都有未知数量的兄弟姐妹和孩子。 我想我需要编写一个递归过程，但我无法将其可视化。

Answer 1

首先，您可能希望TDepartment 的声明与您描述的嵌套结构相匹配：

TDepartment = class
  ID : Integer;
  Name : string;
  ParentDepartmentID : Integer;
  SubDepartments: array of TDepartment;
end;

为了序列化，我建议使用 SuperObject 库而不是内置的 JSON 类：

function TDepartment.Serialize: ISuperObject;
  var Context: TSuperRttiContext;
begin
  Context := TSuperRttiContext.Create;
  try
    Result := Context.AsJson<TDepartment>(self);
  finally
    Context.Free;
  end;
end;

在 cmets 中，OP 提到 TDepartment 包含更多字段，但只有问题中的字段应该被序列化；还必须使用TJSONObject，并且一个部门不知道它的孩子。你可以这样做：

function TDepartment.Serialize2(AllDepartments: TList<TDepartment>): TJSONObject;
  var Department: TDepartment;
      Subdepartments: TJSONArray;
begin
  Result := TJSONObject.Create;
  Result.AddPair(TJSONPair.Create('department_id', TJSONNumber.Create(ID)));
  Result.AddPair(TJSONPair.Create('department_name', Name));
  Result.AddPair(TJSONPair.Create('parent_dept_id', TJSONNumber.Create(ParentDepartmentID)));

  Subdepartments := TJSonArray.Create;
  for Department in AllDepartments do
  begin
    if (Department.ParentDepartmentID <> ID) then Continue;
    Subdepartments.AddElement(Department.Serialize2(AllDepartments));
  end;
  Result.AddPair(TJSONPair.Create('subdepartments', Subdepartments));
end;

Answer 2

我会创建一个平行的树结构，保持原样不变。您当前的结构与您需要的结构相反，因此您可以扫描当前对象并将它们放置在树中。但是在不知道当前结构的情况下很难给出示例代码，但假设所有部门都存在于某种列表中（让我们说称为“部门”）并且“根”部门的父部门 ID 为零，它会有所作为像这样：

unit Unit1;

interface

uses
  System.Generics.Collections;

type
  TDepartment = class
    ID : Integer;
    Name : string;
    ParentDepartmentID : Integer;
  end;

  TDepartmentStructure = class
    ID : Integer;
    Name : string;
    ParentDepartmentID : Integer;
    SubDepartments: TList< TDepartmentStructure >;
    constructor Create( const pBasedOn : TDepartment );
  end;

var
  Department : TObjectList<TDepartment>;

function CopyStructure( pDepartment : TList<TDepartment> ) : TDepartmentStructure; // returns root

implementation

var
  DepartmentStructure : TObjectList<TDepartmentStructure>;

function CopyStructure( pDepartment : TList<TDepartment> ) : TDepartmentStructure;
var
  i, j: Integer;
begin
  // stage one - copy everything
  for i := 0 to pDepartment.Count - 1 do
  begin
    DepartmentStructure.Add( TDepartmentStructure.Create( pDepartment[ i ] ));
  end;
  // now go through and build structure
  Result := nil;
  for i := 0 to DepartmentStructure.Count - 1 do
  begin
    if DepartmentStructure[ i ].ID = 0 then
    begin
      // root
      Result := DepartmentStructure[ i ];
    end
    else
    begin
      for j := 0 to DepartmentStructure.Count - 1 do
      begin
        if DepartmentStructure[ i ].ParentDepartmentID = DepartmentStructure[ j ].ID then
        begin
          DepartmentStructure[ j ].SubDepartments.Add( DepartmentStructure[ i ] );
          break;
        end;
      end;
    end;
  end;
end;

{ TDepartmentStructure }

constructor TDepartmentStructure.Create(const pBasedOn: TDepartment);
begin
  inherited Create;
  ID := pBasedOn.ID;
  Name := pBasedOn.Name;
  ParentDepartmentID := pBasedOn.ParentDepartmentID;
  SubDepartments:= TObjectList< TDepartmentStructure >.Create( FALSE ); // we do NOT own these objects!

end;

initialization
  DepartmentStructure := TObjectList<TDepartmentStructure>.Create( TRUE );

finalization
  DepartmentStructure.Free;

end.

请注意，这仅用于说明目的。你可能不会创建和破坏我拥有的结构。一旦你有了这个结构，你就可以毫无疑问地使用你当前的例程来创建你的 JSON 记录。