mORMot Open Source

mohsenti

Member

Registered: 2015-04-11

Posts: 72

Prevent making not existence classes in JSON Serialization

Hi,

Is there a way to prevent making classes that their object do not exists in the JSON? In my JSON input sometimes the property that is a class does not exists and JSONToObject make a class for that with empty properties, can I set it to do not make an object and just pass nil to it? or I should make a custom serializer?

Here is a sample file:

{
	"ID": 1,
	"Childs": [{
			"ID": 11,
			"Childs": [{
					"ID": 111,
					"Childs": [{}, {}
					]
				}, {
					"ID": 112,
					"Childs": [{}, {}
					]
				}
			]
		}, {
			"ID": 12,
			"Childs": [{
					"ID": 121,
					"Childs": [{}, {}
					]
				}, {
					"ID": 122,
					"Childs": [{}, {}
					]
				}
			]
		}
	],
	"Options": {
		"Name": "Name1"
	}
}

As you can see this is a tree but only parent has "Options" and if I write serializer like below it will make Options class for every child with empty propertises like the output, can I prevent that or I should make a custom serializer? an option would be nice.

program project1;

uses
  Classes,
  SysUtils,
  FileUtil,
  SynCommons,
  mORMot;

type
  TItem = class;
  TItems = array of TItem;

  { TOptions }

  TOptions = class(TPersistent)
  private
    FName: string;
  published
    property Name: string read FName write FName;
  end;

  { TItem }

  TItem = class(TSynAutoCreateFields)
  private
    FID: integer;
    FChilds: TItems;
    FOptions: TOptions;
  published
    property ID: integer read FID write FID;
    property Childs: TItems read FChilds write FChilds;
    property Options: TOptions read FOptions;
  end;

  procedure TestIt;
  var
    it: TItem;
    s: RawUTF8;
  begin
    TJSONSerializer.RegisterObjArrayForJSON([TypeInfo(TItems), TItem]);
    s := StringFromFile('test.json');
    it := TItem.Create;
    ObjectLoadJSON(it, s);
    ObjectToJSONFile(it, 'output.json');
    it.Free;
  end;

begin
  TestIt;
end. 

And the output will be like:

{
	"ID": 1,
	"Childs": 
	[
		{
			"ID": 11,
			"Childs": 
			[
				{
					"ID": 111,
					"Childs": 
					[
						{
							"ID": 0,
							"Childs": [],
							"Options": {
								"Name": ""
							}
						},
						{
							"ID": 0,
							"Childs": [],
							"Options": {
								"Name": ""
							}
						}
					],
					"Options": {
						"Name": ""
					}
				},
				{
					"ID": 112,
					"Childs": 
					[
						{
							"ID": 0,
							"Childs": [],
							"Options": {
								"Name": ""
							}
						},
						{
							"ID": 0,
							"Childs": [],
							"Options": {
								"Name": ""
							}
						}
					],
					"Options": {
						"Name": ""
					}
				}
			],
			"Options": {
				"Name": ""
			}
		},
		{
			"ID": 12,
			"Childs": 
			[
				{
					"ID": 121,
					"Childs": 
					[
						{
							"ID": 0,
							"Childs": [],
							"Options": {
								"Name": ""
							}
						},
						{
							"ID": 0,
							"Childs": [],
							"Options": {
								"Name": ""
							}
						}
					],
					"Options": {
						"Name": ""
					}
				},
				{
					"ID": 122,
					"Childs": 
					[
						{
							"ID": 0,
							"Childs": [],
							"Options": {
								"Name": ""
							}
						},
						{
							"ID": 0,
							"Childs": [],
							"Options": {
								"Name": ""
							}
						}
					],
					"Options": {
						"Name": ""
					}
				}
			],
			"Options": {
				"Name": ""
			}
		}
	],
	"Options": {
		"Name": "Name1"
	}
}

ab

Administrator

From: France

Registered: 2010-06-21

Posts: 14,207

Website

Re: Prevent making not existence classes in JSON Serialization

Those objects DO EXIST in JSON.

A non existing object in JSON is supposed to be a null, AFAIR.

mohsenti

Member

Registered: 2015-04-11

Posts: 72

Re: Prevent making not existence classes in JSON Serialization

Yes but only for parent but not all the childs, I want to only make it for parent not all childs.