deep_pick 0.6.10

Simplifies manual JSON parsing with a type-safe API. No dynamic, no manual casting. Flexible inputs types, fixed output types. Useful parsing error messages

example/deep_pick_example.dart

// ignore_for_file: avoid_print, always_require_non_null_named_parameters, non_constant_identifier_names, omit_local_variable_types
import 'dart:convert';

import 'package:deep_pick/deep_pick.dart';
import 'package:http/http.dart' as http;

Future<void> main() async {
  final json = jsonDecode('''
{
  "shoes": [
     { 
       "id": "421",
       "name": "Nike Zoom Fly 3",
       "manufacturer": "nike",
       "tags": ["nike", "JustDoIt"]
     },
     { 
       "id": "532",
       "name": "adidas Ultraboost",
       "manufacturer": "adidas",
       "tags": ["adidas", "ImpossibleIsNothing"],
       "price": null
     }
  ]
}
''');

  // pick a value deep down the json structure or crash
  final firstTag = pick(json, 'shoes', 1, 'tags', 0).asStringOrThrow();
  print(firstTag); // adidas

  // The unsafe vanilla way with Dart 2.12
  // final firstTag2 = json['shoes']?[1]?['tags'][0] as String?;
  // print(firstTag2); // adidas

  // fallback to null if it couldn't be found
  final manufacturer = pick(json, 'shoes', 0, 'manufacturer').asStringOrNull();
  print(manufacturer); // null

  // you decide which type you want
  final id = pick(json, 'shoes', 0, 'id');
  print(id.asIntOrNull()); // 421
  print(id.asDoubleOrNull()); // 421.0
  print(id.asStringOrNull()); // "421"

  // pick lists
  final tags = pick(json, 'shoes', 0, 'tags')
      .asListOrEmpty((it) => it.asStringOrThrow());
  print(tags); // [nike, JustDoIt]

  // pick maps
  final shoe = pick(json, 'shoes', 0).required().asMapOrThrow();
  print(shoe); // {id: 421, name: Nike Zoom Fly 3, tags: [nike, JustDoIt]}

  // easily pick and map objects to dart objects
  final firstShoe = pick(json, 'shoes', 0).letOrNull((p) => Shoe.fromPick(p));
  print(firstShoe);
  // Shoe{id: 421, name: Nike Zoom Fly 3, tags: [nike, JustDoIt]}

  // falls back to null when the value couldn't be picked
  final thirdShoe = pick(json, 'shoes', 2).letOrNull((p) => Shoe.fromPick(p));
  print(thirdShoe); // null

  // map list of picks to dart objects
  final shoes = pick(json, 'shoes').asListOrEmpty((p) => Shoe.fromPick(p));
  print(shoes);
  // [
  //   Shoe{id: 421, name: Nike Zoom Fly 3, tags: [nike, JustDoIt]},
  //   Shoe{id: 532, name: adidas Ultraboost, tags: [adidas, ImpossibleIsNothing]}
  // ]

  // Use the Context API to pass contextual information down to parsing
  // without adding new arguments
  final newShoes = pick(json, 'shoes')
      .withContext('newApi', true)
      .asListOrEmpty((p) => Shoe.fromPick(p));
  print(newShoes);

  // access value out of range
  final puma = pick(json, 'shoes', 1);
  print(puma.isAbsent); // true;
  print(puma.value); // null

  // Load data from an API
  final stats = await getStats();
  print(stats.requests);
}

/// A data class representing a shoe model
///
/// PODO - plain old dart object
class Shoe {
  const Shoe({
    /*required*/ this.id,
    /*required*/ this.name,
    this.manufacturer,
    /*required*/ this.tags,
    /*required*/ this.price,
  });

  factory Shoe.fromPick(RequiredPick pick) {
    // read context API
    final newApi = pick.fromContext('newApi').asBoolOrFalse();
    final pricePick = pick('price');
    return Shoe(
      id: pick('id').asStringOrThrow(),
      name: pick('name').asStringOrThrow(),
      // manufacturer is a required field in the new API
      manufacturer: newApi
          ? pick('manufacturer').asStringOrThrow()
          : pick('manufacturer').asStringOrNull(),
      tags: pick('tags').asListOrEmpty((it) => it.asStringOrThrow()),
      price: () {
        // when server doesn't send the price field the shoe is not available
        if (pricePick.isAbsent) return 'Not for sale';
        return pricePick.asStringOrNull() ?? 'Price available soon';
      }(),
    );
  }

  /// never null
  final String id;

  /// never null
  final String name;

  /// optional
  final String /*?*/ manufacturer;

  /// never null, falls back to empty list
  final List<String> tags;

  /// what to display as price
  final String price;

  @override
  String toString() {
    return 'Shoe{id: $id, name: "$name", price: "$price", tags: $tags}';
  }

  @override
  bool operator ==(Object other) =>
      identical(this, other) ||
      other is Shoe &&
          runtimeType == other.runtimeType &&
          id == other.id &&
          name == other.name &&
          tags == other.tags;

  @override
  int get hashCode => id.hashCode ^ name.hashCode ^ tags.hashCode;
}

Future<CounterApiStats> getStats() async {
  final response = await http.get(Uri.parse('https://api.countapi.xyz/stats'));
  final json = jsonDecode(response.body);

  // Parse individual fields
  final int/*?*/ requests = pick(json, 'requests').asIntOrNull();
  final int keys_created = pick(json, 'keys_created').asIntOrThrow();
  final int/*?*/ keys_updated = pick(json, 'keys_updated').asIntOrNull();
  final String/*?*/  version = pick(json, 'version').asStringOrNull();
  print('requests $requests, keys_created $keys_created, '
      'keys_updated: $keys_updated, version: "$version"');

  // Parse the full object
  final CounterApiStats stats = CounterApiStats.fromPick(pick(json).required());

  // Parse lists
  final List<CounterApiStats> multipleStats = pick(json, 'items')
      .asListOrEmpty((pick) => CounterApiStats.fromPick(pick));
  print(multipleStats); // always empty [], the countapi doesn't have items

  return stats;
}

class CounterApiStats {
  const CounterApiStats({
    this.requests,
    this.keys_created,
    this.keys_updated,
    this.version,
  });

  final int requests;
  final int keys_created;
  final int keys_updated;
  final String/*?*/  version;

  factory CounterApiStats.fromPick(RequiredPick pick) {
    return CounterApiStats(
      requests: pick('requests').asIntOrThrow(),
      keys_created: pick('keys_created').asIntOrThrow(),
      keys_updated: pick('keys_updated').asIntOrThrow(),
      version: pick('version').asStringOrNull(),
    );
  }
}