TPersonRelation = class(TPersistent)
private
  FName: string;
  FDescription: string;
public
  procedure Assign(Source: TPersistent); override;
published
  property Name: string read FName write FName;
  property Description: string read FDescription write FDescription;
end;

TPersonRelations = TObjectList<TPersonRelation>;

const
  jsonSample =
    '{' +
      '"$type":"TPerson",' +
      '"address":{' +
        '"$type":"TPersonAddress",' +
        '"addressLocality":"Colorado Springs",' +
        '"addressRegion":"CO",' +
        '"postalCode":"80840",' +
        '"streetAddress":"100 Main Street"' +
      '},' +
      '"colleague":[' +
        '"http://www.example.com/JohnColleague.html",' +
        '"http://www.example.com/JameColleague.html"' +
      '],' +
      '"email":"info@example.com",' +
      '"jobTitle":"Research Assistant",' +
      '"name":"Jane Doe",' +
      '"birthDate":"1979-10-12",' +
      '"gender":"female",' +
      '"nationality":"Albanian",' +
      '"relations": ['+
        '{'+
          '"$type":"TPersonRelation",' +
          '"Description": "Brother",'+
          '"Name": "John Doe"'+
        '},'+
        '{'+
          '"$type":"TPersonRelation",' +
          '"Description": "Mother",'+
          '"Name": "Mia Reyes"'+
        '}'+
      '],'+
      '"telephone":"(123) 456-6789",' +
      '"url":"http://www.example.com"' +
    '}';

var
  p: TPerson;
begin
  p := TPerson.Create;
  try
    p.Log;
  finally
    p.Free;
  end;
end;

{
  "$type": "TPerson",
  "Address": {
    "$type": "TPersonAddress",
    "AddressLocality": "Colorado Springs",
    "AddressRegion": "CO",
    "PostalCode": "80840",
    "StreetAddress": "100 Main Street"
  },
  "BirthDate": "1979-10-12",
  "Colleagues": [],
  "Email": "info@example.com",
  "Gender": "female",
  "JobTitle": "Research Assistant",
  "Name": "Jane Doe",
  "Nationality": "Albanian",
  "Relations": [
    {
      "$type": "TPersonRelation",
      "Description": "Brother",
      "Name": "John Doe"
    },
    {
      "$type": "TPersonRelation",
      "Description": "Mother",
      "Name": "Mia Reyes"
    }
  ],
  "Telephone": "(123) 456-6789",
  "URL": "http://www.example.com"
}

Loading a generic list

To understand how to load JSON data containing an array which will be mapped onto a generic list, please head over to the previous blog post explaining which interfaces are required to handle and load JSON with and without the "$type" properties. The loading mechanism for a generic list is exactly the same as with a TCollection.

Working with a TDictionary<K, T>

TDictionary<K, T> is supported, but the key type is restricted to a string. Let's take a look at the following example.

TMyObject = class(TPersistent)
private
  FMyProperty: string;
published
  property MyProperty: string read FMyProperty write FMyProperty;
end;

TMyDictionary = TObjectDictionary<string, TMyObject>;

We'll add 2 objects respectively in key 1 & 2.

var
  d: TMyDictionary;
  o: TMyObject;
begin
  d := TMyDictionary.Create;

  try
    o := TMyObject.Create;
    o.MyProperty := 'Property Value 1';
    d.Add('1', o);

    o := TMyObject.Create;
    o.MyProperty := 'Property Value 2';
    d.Add('2', o);

    d.Log;
  finally
    d.Free;
  end;

[
  {
    "2": {
      "$type": "TMyObject",
      "MyProperty": "Property Value 2"
    }
  },
  {
    "1": {
      "$type": "TMyObject",
      "MyProperty": "Property Value 1"
    }
  }
]

Supported generic types

• TList<TObject>, or TObjectList<TObject>
• TList<string>
• TList<Integer>
• TList<Double>

In the following sample, we'll demonstrates how to use and persist a generic TList<Integer>.

TMyIntegerList = TList<Integer>;

var
  l: TMyIntegerList;
begin
  try
    l := TMyIntegerList.Create;
    l.Add(50);
    l.Add(6);
    l.Add(978);
    l.Add(20);
    l.Log;
  finally
    l.Free;
  end;
end;

[
  50,
  6,
  978,
  20
]

Next up will be how to use the undo/redo manager, so stay tuned for more to come! As always, please leave a comment or if you have any questions, don't hesitate to ask us!