Prefer deep_pick for JSON Parsing

Prefer deep_pick for JSON Parsing

Parse JSON with package:deep_pick instead of code generation or casting the Map from jsonDecode by hand, because it is type safe, null aware and needs no build_runner.

Use package:deep_pick for parsing JSON instead of code generation solutions like json_serializable or manual handling of Map<String, dynamic> from jsonDecode()

Why deep_pick?

• No build_runner required - works at runtime
• Type-safe with fixed output types regardless of input
• Handles null safety gracefully - each method explicitly declares null behavior
• Clear error messages distinguishing between absent keys and null values
• Supports nested access with pick(json, 'user', 'address', 'city')
• Automatic type conversions (String to int/double, bool strings, etc.)
• Range-safe list access - out-of-bounds returns null instead of crashing

Available Methods

Basic Example

Use fromPick factory constructor pattern for parsing lists:

import 'package:deep_pick/deep_pick.dart';

class User {
  factory User.fromPick(RequiredPick pick) {
    return User(
      name: pick('name').asStringOrThrow(),
      age: pick('age').asIntOrThrow(),
    );
  }
}

// Parse list of users
final users = pick(json, 'users').asListOrEmpty((pick) => User.fromPick(pick));

Rekord Pattern with fromPick

When using the Rekord pattern, add a fromPick factory that delegates to fromData. Call pick.asMapOrThrow() directly, no need to wrap it in Map<String, Object?>.from() since asMapOrThrow() already returns Map<String, Object?>.

// ✅ Good
factory WorkoutSummary.fromPick(Pick pick) {
  return WorkoutSummary.fromData(pick.asMapOrThrow());
}

// ❌ Bad - redundant Map.from() copy
factory WorkoutSummary.fromPick(Pick pick) {
  return WorkoutSummary.fromData(Map<String, Object?>.from(pick.asMapOrThrow()));
}

Custom Types with let

Use letOrNull/letOrThrow for custom type transformations:

final UserId id = pick(json, 'id').letOrNull((pick) => UserId(pick.asString()));
final status = pick(json, 'status').letOrThrow((pick) => Status.fromString(pick.asString()));

https://pub.dev/packages/deep_pick