IJsonObject.Contains

Syntax

Contains(Key: String): Boolean;

Parameters

Key. Name of the element used as a key.

Description

The Contains property returns whether there is an element with the specified name.

Comments

Available values:

True. The element with the specified name is contained in child elements of the current object.
False. The element with the specified name is not contained in child elements of the current object.

Example

Executing the example requires the JSON file: D:\Work\Json\testfile.json.

Sub UserProc;
Var
    Doc: IJsonDocument;
    NewJSON: IJsonObjectBuilder;
    JSON: IJsonObject;
    Element: Boolean;
    Name: String;
Begin
    // Load JSON structure from the specified file
    Doc := New JsonDocument.Create;
    Doc.ReadFromFile("D:\Work\Json\testfile.json");
    JSON := Doc.RootElement.AsObject;
    // Check if the structure contains element named Value
    Name := "Value";
    Element := JSON.Contains(Name);
    If Element Then
        Debug.WriteLine("Element is contained in JSON structure");
    // Add the Value element with the 100 value if it is absent in the structure
    Else
        NewJSON := New JsonObjectBuilder.Create;
        AddExistElement(JSON, NewJSON);
        NewJSON.AddInteger(Name, 100);
        Doc := New JsonDocument.Create;
        Doc.RootElement := NewJSON.Build;
        // Save changes in file
        Doc.WriteToFile("D:\Work\Json\testfile.json");
    End If;
End Sub UserProc;

Sub AddExistElement(OldJson: IJsonObject; Var NewJson: IJsonObjectBuilder);
Var
    i, c: Integer;
    Element: IJsonElement;
Begin
    c := OldJson.Count;
    For i := 0 To c - 1 Do
        Element := OldJson.ItemByIndex(i);
        Select Case Element.GetType
            Case JsonElementType.Boolean: NewJson.AddBoolean(OldJson.Property_(i), Element.AsBoolean);
            Case JsonElementType.Double: NewJson.AddDouble(OldJson.Property_(i), Element.AsDouble);
            Case JsonElementType.Integer: NewJson.AddInteger(OldJson.Property_(i), Element.AsInteger);
            Case JsonElementType.NullValue: NewJson.AddNull(OldJson.Property_(i));
            Case JsonElementType.String: NewJson.AddString(OldJson.Property_(i), Element.AsString);
        End Select;
    End For;
End Sub AddExistElement;

After executing the example, a new element named Value is added to the JSON structure of the testfile.json file if the structure does not contain an element with this name. If an element named Value is contained in the JSON structure, the console displays the corresponding message.