LoadFromString

procedure LoadFromString(const aJSONString: String);

Example

procedure ScriptEvent(var Value: variant);
var
  Payload: TJSONObject;
begin
  Payload := TJSONObject.Create;
  try
    Payload.LoadFromString('"reference":"DEMO-1001","quantity":2');
    Value := Payload.AsString;
  finally
    Payload.Free;
  end;
end;

Usage

LoadFromString replaces values from a complete object or auto-wrapped member fragment, with first-character whitespace and empty-input traps.

Additional Technical Info

LoadFromString accepts either a complete object beginning with { or a field fragment. For any nonempty input whose first character is not {, it prepends { and appends } before assigning inherited AsString.

The first-character test happens before trimming. A fragment with leading whitespace is wrapped usefully, but a complete object preceded by whitespace is wrapped as a nested fragment and then fails because the outer object parser expects a quoted field name. The direct CreateFromString path does not wrap and accepts leading JSON whitespace.

Empty input is assigned without wrapping. TJSONObject.DoSetAsString first clears the inherited private null-storage bit, but the parser then reads no value and existing children remain. The internal bit change has no public effect because TJSONText.IsNull is fixed false and object serialization ignores that storage. This is not a reliable reset operation—use Erase when the values must be removed.

Malformed, wrong-type or wrapped-invalid input raises. Parsing occurs before replacement, so old children remain on those errors; only the unobservable private bit has already been cleared. A successful load frees the old graph and deep-clones parsed values.

Duplicate names and trailing input are accepted. \uXXXX, exponent-only numbers and locale-sensitive decimals retain the shared reader defects. A successfully parsed empty object later serializes as }.

External references

• RFC 8259 section 4: Objects

Created 2026-07-20