DataSourceTrace.fromJson constructor

DataSourceTrace.fromJson(Map<String, Object?> json)

Reads what toJson wrote. Throws a DataSourceTraceFormatException when steps or values are missing, differ in number, or an entry is not a step number and a map. The order of steps is not checked.

Implementation

factory DataSourceTrace.fromJson(Map<String, Object?> json) {
  final rawSteps = json['steps'];
  final rawValues = json['values'];
  if (rawSteps is! List || rawValues is! List) {
    throw const DataSourceTraceFormatException(
      'the trace has no steps or no values',
    );
  }
  if (rawSteps.length != rawValues.length) {
    throw const DataSourceTraceFormatException(
      'the trace has a different number of steps and values',
    );
  }
  final steps = <int>[];
  final values = <Map<String, Object?>>[];
  for (var i = 0; i < rawSteps.length; i++) {
    final step = rawSteps[i];
    final value = rawValues[i];
    if (step is! num || value is! Map) {
      throw const DataSourceTraceFormatException(
        'an entry is not a step number and a value map',
      );
    }
    steps.add(step.toInt());
    values.add(Map<String, Object?>.unmodifiable(value));
  }
  return DataSourceTrace._parts(steps, values);
}