Handling JSON NULL values in Delphi

There is a quite frequent question about how to correctly handle NULL values in Delphi using System.Json.TJSONObject.

Handling existing values, in this example, the array of „customers“ is fairly easy:

{"customers":[{"name":"Olaf"},{"name":"Big Bird"}]}

But what, if the array is „null“?

{"customers":null}

	const
	CUSTOMERS = '{"customers":[{"name":"Olaf"},{"name":"Big Bird"}]}';
	CUSTOMERS_NULL = '{"customers":null}';
	procedure TForm39.Button1Click(Sender: TObject);
	var
	LContainer: TJSONValue;
	LCustomers: TJSONArray;
	begin
	//Here, the value is not nil, so you can just go ahead with GetValue
	LContainer := TJSONObject.ParseJSONValue(CUSTOMERS);
	try
	LCustomers := LContainer.GetValue<TJSONArray>('customers');
	Assert(LCustomers.Count = 2);
	finally
	FreeAndNil(LContainer);
	end;
	// If the value can be null though, then specify a default - which can be "nil"
	LContainer := TJSONObject.ParseJSONValue(CUSTOMERS_NULL);
	try
	LCustomers := nil;
	LCustomers := LContainer.GetValue<TJSONArray>('customers', nil);
	Assert(LCustomers = nil);
	finally
	FreeAndNil(LContainer);
	end;
	// There is also TryGet, but that's probably slower and less convenient
	LContainer := TJSONObject.ParseJSONValue(CUSTOMERS_NULL);
	try
	LCustomers := nil;
	LContainer.TryGetValue('customers', LCustomers);
	Assert(LCustomers = nil);
	finally
	FreeAndNil(LContainer);
	end;

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